Incorrect resolution after trusted.gpg deleted

[Luttim]

Trying to solve a key problem with the latest release of an app, I have deleted the trusted.gpg file (and hidden file of the same name) from /etc/apt/
System still appears to be working properly, however graphics during boot process (before log in screen) now have the incorrect resolution.
Is there anything I should be re-installing after deleting that file?

Mint Cinnamon 20.3

EDIT: Now shutting down does not seem to work.
I choose Quit from Menu > Shut Down, but it only logs me out instead of shutting down

[Cosmo.]

Use the built-in safety belt of Mint: Restore a previous Timeshift snapshot.

[Luttim]

I have no timeshift snapshots available. Must have turned it off to save space.

[Cosmo.]

Now you have space, but a defective system. Safety belts have a meaning. Deciding to not using them can be a final decision. No profi (race driver, airplane pilots) would do this. Consider this the next time.

[djph]

Trying to solve a key problem with the latest release of an app, I have deleted the trusted.gpg file (and hidden file of the same name) from /etc/apt/
Is there anything I should be re-installing after deleting that file?

the entire system. You've hosed your software manager.

[Luttim]

Well, boot is now working correctly again, and I just tried installing something from software manager, which worked.

I ran the following command, which might have done the trick:
sudo apt-get install --reinstall linuxmint-keyring ubuntu-keyring