others have provided you with a some good answers so i only mean to share that; if none of those work for you; you can google search key mapping on google to find even more alternatives to try out.
Go into system settings > mouse > select your mouse > rebind buttons
Thank you. These are the settings available to me, but I do not see the option to rebind buttons.
Ah, you’re on Xorg. This feature is only available in the Wayland session
Woah, thank you so much! This is actually really fricken cool and surprisingly easy to setup!
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
Thank you for that, I had no idea it existed.