SU does not respond to letters/numbers on keyboard input, can't type password
 

I don't know when this started, but both su and sudo, asking password and whatever I type just does not register. Enter does respond, but of course says "wrong password".
There are no problems entering it in GUI (say "run with elevated" on right click in file manager).

Noob here. Requesting the easiest solution possible, preferably in GUI.

Did you create a root password?

Are you using the correct password? sudo requires your admin users password,
su requires the root password.

Most common cause is to have number lock enabled - I hate distros that do it! ;)

or probably it is a language specific issue, but without details hard to say anything

Based upon the complete and accurate specs. you have not provided, is it possible that your notebook computer's Fn key and/or Numlock key assignments have been accidentally altered from the state they were formerly in when the password was first conceived?

Dell notebook, Fn key, Numlock key, wrong password at DuckDuckGo
https://duckduckgo.com/?q=Dell+noteb...=v351-1&ia=web

BTW. A service manual and a UEFI/BIOS guide for your computer are worth searching for.

 

IlanSh posted the exact same question on Linux Mint forums, where the issue seems [partially] resolved.

https://forums.linuxmint.com/viewtopic.php?t=388842

sudo is asking for who's password?

Issue resolved, details:
 

Thanks everyone!

The solution is:
The file is /etc/sudoers.d/0pwfeedback and its content is only 1 line: Defaults pwfeedback
Note:
All files inside /etc/sudoers.d/ have to be owned by root:root and their permissions have to be r--r-----.

This was generously provided by karlchen.

Cheers!