It's the kind of thing you don't realize you use a lot until you don't have it anymore. Might be helpful to someone else, it filtered me pretty hard when I tried linux the first couple of times. In Firefox the about:config key is, (I hope I didn't fuck up the code brackets)
Set to true:
general.autoscroll
Set to false
middleclick.paste
For flatpak programs, edit your .desktop file that launches the program of your choosing either by rightclicking its icon or browsing to ~/.local/share/applications/ and editing it there instead, add this to the end of the command line arguments
--enable-blink-features=MiddleClickAutoscroll
there's also yet another setting in Plasma that controls gtk mouse scrolling
Plasma Settings -> Input & Output -> Mouse -> tick "Hold down middle button and move mouse to scroll"
There you go. Now you don't have to wade through a sea of assholes claiming the middle mouse button should be a paste button, insisting that you're using your PC wrong if you don't like this default behavior. You'll be able to autoscroll without worrying about dropping random text into input boxes this way. It's not completely foolproof but it works well enough for me. There's probably still some random fuckass program that still doesn't autoscroll but this covers the vast majority of them.
