Solved by bsherman in this ublue forum link

Hello, and welcome! share my personal experience with printers on Silverblue/Bluefin. When go to GNOME's "Settings" app and find the "Printers" section, even on a fresh installation, see my HP LaserJet listed.. it's "just there". However... it does NOT "just work". have to do the following:

1. click "Unlock" in the top-right corner of the "Printers" view

2. click "Add Printer.." now available after unlocking..

3. wait until my printer shows up, if wait long enough, multiple entries show, but I select the first entry for my printer, then click "Add"

4. after a moment, a second entry for my printer shows up in the "Printers" list. in my case, this shows the "Model" name plus driverless" at the end.

Now, this printer is visible in apps like LibreOffice or Firefox. hope this helps you. I've never dug deep to find out why the system behaves like this, but it works for me.

My Brother just works on Bazzite KDE.

So prolly a Gnome issue?