try the fix from here https://support.mozilla.org/en-US/questions/1012145

Let me know if it works.

Thank you for your comment. Unfortunately this did not solve the problem.

layers.acceleration.disabled true I had already set.

gfx.direct2d.disabled was not existing in my profile configuration. I gave it a try by adding it. Now the result tab from the global search is not black anymore, but the same blue-ish white as the rest of the page.

But still I can't see the results. I know this feature from running Thunderbird on Windows where it works great. I am desperate to get it to work. Any other ideas?

sounds like there are two issues.

The graphics is one and the global search is another.

Are your searches actually returning results? It takes time to build the global search database. It can also be corrupted sometime and need to be deleted.

But which is this the case here. I do not know. Check in the tools menu > activity manager. Anything there about indexing? If nothing, go to the help menu and select troubleshooting information. Click the show profile button and close Thunderbird delete the global-messages-db. sqlite file and restart Thunderbird. Now there should be some indexing.

Deleting the global-messages-db. sqlite file indeed solved the problem.

I copied yesterday the complete Thunderbird folder with profiles etc to a new location to have it available on Ubuntu. I guess that somehow messed up the database file. I see the database file now growing.

Thank you so much for your help!