I'm trying to use the procedure @ unetbootin.github.io/linux_download.html to make a grub repair USB live tool. I enter #add-apt-repository ppa:gezakovacs/ppa and see "Warning: apt-key is deprecated...gpg: no valid Open PGP data found." When I then enter #apt-get update, I see more error messages, including " The repository ... does not have a Release file. Updating from such a repository can't be done securely."
Can I get unetbootin some (other) way? It's the most recommended tool; maybe there's another one I should use?

If I had to get it I would get it direct form the source https://unetbootin.org/

By preference, I would drop install images onto a VENTOY usb drive instead, but you have not made clear your objective.

Unetbootin is specifically NOT recommended by Debian. Another alternative is Balena-Etcher. https://www.balena.io/etcher/

Adding a PPA is not a good idea. Shades of "Don't Break Debian", https://wiki.debian.org/DontBreakDebian/

Hello
unetbootin has been on the Not on for Debian for a long time now, many years, what you need to do is go to the software center of the distro your using and get from there the software that works properly, Do Not go all over the WWW to find software and download from wherever.

This is Linux supplying it's safe to use out of the Synaptic or Discover centers or use the terminal.

This is not Microsoft where to install anything you need to run the WWW jungle.

If it isn't in the shop it isn't in my computer.


Suggestion this is the way I find what I need
goto here

https://alternativeto.net/software/compare-it/

type unetbootin in the searchbox

compare with what is in Synaptic or Discover for your distro

Safe

Just had a look and this is much better more choices to compare with

https://alternativeto.net/browse/sea...Image%20Writer

All the best
artytux