Same after Help > Troubleshoot Mode?

Yes, the troubleshoot mode is far away from solving this issue. It is only for extensions. I do not use any additional functions, only the original thunderbird.

Yes, the troubleshoot mode is far away from solving this issue. It is only for extensions. I do not use any additional functions, only the original Thunderbird.

No it is not only for extensions. It also changes video settings and disables hardware acceleration. That does not help if it is already disabled however and now needs to be enabled. It is a coin toss if enabled or disabled or even if you would notice the difference in hardware acceleration, but it has been very problematical over the years so changing the setting is sort of a standard try.

You appear to be using windows 10 or 11. Looking at the image, I see three distinct black areas, but I also do not see the global search box on the toolbar.

1. Do you have global search disabled in settings?
2. Do you have a userchrome.js file to modify Thunderbird layout?
3. Have you at some point modified modified the hidden preference layout.css.devPixelsPerPx. Please use the config editor to confirm the setting is still default.
4. on your windows computer go to settings and navigate to system > display > advanced.
5. What are the color settings given there? in terms of depth, format and space. ( I am looking for something a bit out of the ordinary here. So nothing is "wrong")
6. Do you have more than one display listed there? If so are all displays showing the same colour depth and RGB settings?

Yes, the troubleshoot mode is far away from solving this issue. It is only for extensions. I do not use any additional functions, only the original thunderbird.

Is there confusion about whether suggestions from top contributors is good advice?