A while ago, to set up a secondary display again for my ThinkPad T570, I spent a lot of time troubleshooting external monitor issues.
I initially used an older monitor. Because it primarily offered a VGA port, I had to connect via an HDMI-to-VGA adapter. When that setup started causing issues like a black screen on the secondary display, I bought a Type-C-to-VGA cable, hoping to bypass the original HDMI-to-VGA link.
I thought simply changing the connection method would fix the problem, but after connecting the new Type-C-to-VGA cable, Ubuntu did not even detect the secondary monitor.
On July 30, 2026, I conducted a fairly deep troubleshooting session for this. I checked everything from Wayland, DRM, USB Type-C, and UCSI all the way to the BIOS and Thunderbolt Controller, and along the way, I upgraded the ThinkPad T570 BIOS from 1.23 to 1.54.
Although I did not restore Type-C video output in the end, I was basically able to confirm that this was no longer an ordinary Ubuntu dual-screen configuration issue.
My final decision at the time was:
Temporarily stop trying to fix the Type-C / Thunderbolt link and simply switch to a monitor with native HDMI support as the secondary display.
The new monitor is now in use, and dual-screen is finally working properly.
1. Giving up on VGA conversion this time
The old monitor was limited by its ports; no matter how I connected it, I could not get around VGA.
Initially, I used HDMI-to-VGA:
ThinkPad T570 HDMI → HDMI-to-VGA adapter → VGA → secondary monitor.
Later, to bypass the original adapter, I tried Type-C-to-VGA:
ThinkPad T570 USB-C → Type-C-to-VGA → VGA → secondary monitor.
The second option appeared to simply change the port on the computer side, but it actually involved USB-C, DisplayPort Alt Mode, and the conversion of a digital signal to an analog VGA signal.
This is why, once the Type-C / Thunderbolt link itself developed an issue, the end result was that the secondary screen was completely undetectable.
When choosing a new monitor this time, I simply stopped trying to accommodate VGA.
The new monitor natively supports HDMI, so the current connection method is very simple:
ThinkPad T570 HDMI → HDMI cable → Monitor HDMI2.
The computer side uses the T570’s built-in HDMI port, and the monitor side connects to the HDMI2 port.
There are no video converters in between anymore.
2. After connecting the cable, Ubuntu dual-screen immediately returned to normal
The truly relieving part is that this time there is almost nothing left to write up as “troubleshooting steps.”
After connecting the HDMI cable and turning on the monitor, Ubuntu was able to use the external display properly.
I did not encounter the issue of the system completely failing to detect the secondary screen again, nor did I need to continue checking UCSI, Thunderbolt, DRM, or BIOS settings.
In other words, it finally reached the state I originally wanted:
Plug in the cable, and use it.
Here, I plan to use this actual photo of my dual-screen working environment.
The photo directly shows that both the ThinkPad T570 and the new monitor are displaying content normally. This better reflects the actual result this article aims to record than continuing to post BIOS or terminal screenshots—this dual-screen setup is back in practical use.
3. It can now be confirmed that Ubuntu itself is not unsuitable for dual-screen
While troubleshooting the Type-C-to-VGA issue on July 30, I once had a question:
Why does simply adding a secondary screen to Ubuntu become so troublesome?
Is it because I am using Linux that dual-screen compatibility is so complex?
Now that I am back to a direct HDMI connection, this question actually has a very direct answer:
No.
It is still the same ThinkPad T570, and it is still the Ubuntu desktop environment.
The only difference is that the connection method changed from Type-C-to-VGA to a direct HDMI connection.
As a result, dual-screen works immediately.
This at least shows that the T570’s current HDMI output, the Intel display system, and Ubuntu’s dual-screen management can all work properly.
Therefore, the previous failure cannot simply be attributed to “Ubuntu does not support dual-screen” or “Wayland causes the secondary screen to be unavailable.”
The real anomaly lay in the USB-C / Thunderbolt / DisplayPort Alt Mode link at the time.
4. The new monitor also further validates the previous troubleshooting direction
During the previous troubleshooting process, a few phenomena remained highly abnormal.
For example, the T570’s USB-C port itself could be recognized by Linux, but after plugging in the Type-C-to-VGA adapter, the corresponding Type-C partner did not appear properly.
The DRM layer’s DP interface also remained in a disconnected state.
Later, even after setting the boot display device to USB Type-C in the BIOS, the secondary monitor still did not receive a video signal before Ubuntu booted.
Finally, I used boltctl to successfully request forced Thunderbolt power-on, but the Thunderbolt Controller still did not enumerate properly.
At that time, I could only reach a relatively cautious conclusion:
The ThinkPad T570’s USB-C / Thunderbolt subsystem might have an underlying anomaly.
Now that the direct HDMI connection works properly, it serves as an additional validation result.
If the problem lay with Ubuntu’s overall external display functionality, the Intel graphics driver, or all video outputs on the machine, then switching to HDMI might not have recovered so smoothly.
The facts now prove:
- The T570’s HDMI output works normally;
- Ubuntu can properly recognize the external monitor;
- The dual-screen desktop works normally;
- The problem is more concentrated on the previously used USB-C / Thunderbolt video output link.
Therefore, although the previous troubleshooting did not actually fix Type-C, the direction was at least not a waste of effort.
5. Why I ultimately did not continue repairing Thunderbolt
In theory, the previous troubleshooting did not reach a true dead end.
The ThinkPad T570 has a corresponding Thunderbolt firmware update available, and what I upgraded at the time was the System BIOS, not the Thunderbolt Controller’s own NVM firmware.
If I continued digging deeper, I could consider setting up a Windows environment and trying whether Lenovo’s official Thunderbolt firmware tool could recognize and restore the Controller.
From a technical research perspective, there is certainly still room to keep tinkering.
The problem is that my actual need is simply:
To have a secondary monitor that works stably.
If fulfilling this need requires continuing to set up Windows, researching Thunderbolt NVM, attempting to restore the controller, or even further troubleshooting motherboard hardware, the time cost would clearly exceed the actual benefit.
And the T570 itself has a working HDMI port.
In this situation, bypassing the faulty USB-C video output is obviously more practical than continuing to repair it.
6. Sometimes you should solve the need, rather than obsessing over fixing the fault
This experience made me clearly realize one thing.
When doing technical troubleshooting, it is easy to fall into a habit:
Once a fault is found, you want to keep chasing it until you get a completely clear root cause.
For example:
Why did the Thunderbolt Controller fail to enumerate?
Is the NVM firmware actually damaged?
Is there an issue with a motherboard chip?
Why did the Type-C-to-VGA completely fail to establish DisplayPort Alt Mode?
These questions are certainly worth researching in themselves.
But if the original goal was just to get a usable secondary screen, then whether it is worth continuing to research these questions needs to be considered separately.
The solution I ultimately adopted this time is actually very ordinary:
Switch to a monitor with HDMI, and connect directly via HDMI.
No new drivers, no complex configuration, no going back into the BIOS, and no continuing to check kernel logs.
But it actually solved the need.
From this perspective, sometimes “bypassing the problem” does not mean troubleshooting failed.
If a simpler, more stable solution can achieve the original goal, then it is a reasonable solution in itself.
7. Shifting from analog VGA to a pure HDMI digital connection
The new connection setup also has an aspect I am quite satisfied with:
Completely getting rid of VGA.
VGA is an analog video interface, while HDMI is a digital interface.
In the past, whether using HDMI-to-VGA or Type-C-to-VGA, an extra conversion was required.
The new setup connects the computer’s HDMI directly to the monitor’s HDMI2, keeping the entire video link digital.
For my daily use of browsers, WordPress, VS Code, terminal, and other desktop applications, a 1920×1080, 60Hz digital display connection is completely sufficient.
At the same time, removing a converter also removes a potential point of failure, compatibility issues, or poor contact.
For long-term use, I now also lean towards:
If a monitor can directly use digital interfaces like HDMI or DisplayPort, try not to continue relying on VGA for the sake of compatibility with old devices.
8. After restoring dual-screen, actual use is much more convenient
When the secondary screen was unavailable, many windows could only be piled up on the ThinkPad T570’s built-in screen.
This was not a big deal for ordinary web browsing or simple tasks, but once I simultaneously used a browser, terminal, VS Code, or WordPress backend, switching windows on a single screen became noticeably more cumbersome.
Now that the secondary screen is back, I can separate different types of work again.
For example, the larger monitor is mainly used for browsers, web content, or windows that require a larger viewing area, while the ThinkPad’s own screen can continue to hold other tools.
This change is not some complex performance boost, but for someone who uses a computer for long hours every day, the convenience brought by dual screens is still very obvious.
And compared to constantly encountering black screens and non-detection before, the most important thing now is:
It finally works stably.
9. Looking back at this secondary screen issue
The whole process actually went through several stages.
It started with the old monitor connected via HDMI-to-VGA, which later suffered a black screen on the secondary display.
Next, I tried switching to Type-C-to-VGA, only to find that Ubuntu could not detect the monitor at all.
Then I began deep troubleshooting of Type-C / Thunderbolt, checking all the way through BIOS, UCSI, and forced controller power-on, and incidentally upgrading the T570’s BIOS from 1.23 to 1.54.
In the end, I did not continue chasing the Thunderbolt firmware, but decided to simply switch to an HDMI-supported monitor.
Now, after connecting the new monitor directly via HDMI, dual-screen is working normally.
Looking at the final result, this is probably the approach that suits me best.
Not every underlying hardware issue must receive unlimited time invested just to “completely solve” it.
Especially when the device has been used for years and a simple, reliable alternative path exists, adjusting the plan in a timely manner is often more worthwhile than continuing to obsess over the original connection method.
10. Conclusion
The ThinkPad T570’s HDMI port is now directly connected to the new monitor’s HDMI2 port, and Ubuntu dual-screen is back to normal.
The Type-C / Thunderbolt issue I kept tinkering with before has not been truly fixed, but it temporarily no longer affects my actual use.
The solution that actually solved the problem in the end did not involve complex technology:
Just a direct HDMI connection.
After going through the old secondary screen’s black screen, HDMI-to-VGA, Type-C-to-VGA, BIOS upgrades, and Thunderbolt troubleshooting, I ultimately returned to the simplest connection method.
For me, the biggest takeaway from this experience is not how many Linux troubleshooting commands I learned, but:
First clarify what actually needs to be solved.
If the goal is just to use dual screens stably, then choosing a simple, reliable, low-maintenance connection method better fits the actual need than investing a lot of time to prove whether a certain old port can still be fixed.
Dual-screen is now available again.
As for the ThinkPad T570’s still-questionable USB-C / Thunderbolt issue, I will leave it until there is an actual use case to decide whether to continue researching it.