Tor Browser on Debian 10 Buster Shows a Black Screen
A one-liner can fix this

Tor browser window on Debian 10 Buster was all-black after the recent update. It’s a known bug and is being tracked as bug #942901 on Debian bug tracking service.
Tor browser window shows only black screen because the default apparmor
profile does not allow write access to /dev/shm/org.mozilla.ipc.*.*.
There’s an easy fix for this: open your text editor of choice and run the following command:
mousepad /etc/apparmor.d/local/torbrowser.Browser.firefox
I used the Mousepad text editor for this purpose. You can any text editor though. Just replace mousepad in the aforementioned command with your preferred text editor.
torbrowser.Browser.firefox file will open in your text editor. Now paste the following and save the file:
owner /{dev,run}/shm/org.mozilla.*.* rw,
Now open terminal and run the following command:
systemctl restart apparmor
This self-explanatory command restarts the apparmor and solves this issue. Now open Tor browser and see your problem is solved.
