Auto-Update to most recent Tor-Browser: Message about profile not readable, all windows black afterwards
After auto-updating to 9.0 on Debian Buster with KDE Plasma, I got an error message popup instead of the "connect" window when starting that said something about my profile not being readable.
However I only saw the message when clicking somewhere into the popup window and copypasting the text - as the window was just a black rectangle, nothing visible except the KDE-Plasma-styled titlebar and window frame.
After closing the window and retrying to start Torbrowser several times, every Window was just all black, both the connection and the browser window. I tried re-installing both 9.0 and an older 8.0.3 to the same location and removing all mozilla/torbrowser related files in various locations (~/.local/share, ~/.mozilla, ~/.config/) which didn't help, the windows stayed black.
Torbrowser is installed to ~/.local/share/torbrowser/tbb/x86_64/tor-browser_en-US, it was originally installed using the debian torbrowser-launcher packet from stretch-backports and patched forward until now.
Interestingly, extracting the torbrowser download to a different location and running it in that fresh install location doesn't have black windows anymore and seems to work normally. Of course then my config and addons are gone.
Might be related to some apparmor problems; however, removing the torbrowser-launcher packet which should change apparmor configs doesn't help.