I asked a friend who uses nobara and he says
Oh I know what they're running into
They're using the rpm which is copied from fedora upstream
Fedora ships with firefox by default and sets the home page to the fedoraproject site
Not sure what they're doing to trigger it to revert though
Nobara moved to chromium as the stock browser in order to have compatibility with steamdeck plugins, anyways
but all you do is just install firefox manually and go home
I'm not sure if that user is using the firefox rpm or flatpak
I use the flatpak with no issues, so
¯\(ツ)/¯
tl;dr as a solution for them, try the flatpak of firefox and see if it does the same thing
flatpaks have better security anyways, because they're sandboxxed away from being able to access the entire system