Hi All,
I’ve just remove an unwanted repo, with help from this forum, and after I rebooted, all the Fedora Workstation 42, (Gnome 48.2.) system apps come up as just a blank screen:
System Monitor, File Manager, Terminal, Software, Text Editor, Settings.
All my own Flathub downloaded software, Floorp, Logseq, Darktable etc, they all open and function as normal. The Extension Manager opens as normal.
The original problem was, which was resolved, I was getting a missing GPG message in the terminal. I had installed VirtualBox from rpmfusion, but earlier I had installed VB from it’s own website. I won’t repeat all the details, but I removed the VB repo and the GPG message was cleared. Here is the thread:
VirtualBox installed but missing GPG signature - Fedora Discussion
But then, after I rebooted, the above mentioned system apps are all blank (similar to this screenshot). Here is a screenshot of the Text Editor:
Note: the terminal still functions, even though it is blank. For example I typed in sudo reboot, added the password (all ‘blindly’), Enter, and it reboots. Even though I’m only seeing a completely blank Terminal screen.
I have run DNF system update, and in GRUB gone back to an earlier option (newbie here, I think that’s what it is, press Shift on boot), but nothing changed.
As my regular browser is working, I have downloaded from flathub, Console (terminal) and Dolphin (file manager) and they function as expected.
Any and all suggstions gratefully received 
Edit: forgot to say, I ran dnf repolist, and using the keyboard shortcuts, select all, copy, copied into OnlyOffice, and the complete repo list is there, even though the Terminal is completely blank.
Thank you.