169
Firefox 121.0.1 released
(www.mozilla.org)
A place to discuss the news and latest developments on the open-source browser Firefox
Actually KDE has a feature where you can set which display any app shows on, and if it should be maximized horizontally or vertically or both.
I use that for Firefox specifically, as I always like it on my secondary monitor.
Just right click on the title bar of any application to get to those settings.
(I'm using KDE on Fedora.)