If you’ve got Logitech, check out Piper (which is really just a GUI wrapper for libratbag). After a lot of searching, this ended up being the solution I went with.

EDIT: pulled up the link but then forgot to paste it, sorry! https://github.com/libratbag/piper

KDE is Windows 98, full of fun customizations, but unpolished in odd ways no matter what you do.

Absolutely perfect. And part of why I’ve grown to love it.