To be honest, you don't need to backspacing on the address bar! Just start typing and you'll be okay. It is the same with about:preferences too.

No, it appends to "about:home", it would work if it was highlighted though.

Now it's intermittent. But I found another way, press F6 twice then write :)

Alt+Home works for me in Nightly.

Are you in X11 or Wayland?

Try downloading another copy of Firefox and run it from the folder. Do not sign into your Firefox account and see if you have the same issue.

https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

Operating System: openSUSE Tumbleweed 20211202 KDE Plasma Version: 5.23.4 KDE Frameworks Version: 5.88.0 Qt Version: 5.15.2 Kernel Version: 5.15.5-1-default (64-bit) Graphics Platform: X11 Processors: 4 × Intel® Core™ i7-4810MQ CPU @ 2.80GHz Memory: 31.0 GiB of RAM Graphics Processor: Mesa DRI Intel® HD Graphics 4600

Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or userChrome.css is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems