When I upgraded my computers to Ubuntu 20.04, I noticed a weird problem with OBS when using an old Wacom Bamboo tablet (because, have you ever tried to use OBS without a pointing device?). I couldn't actually click anything! The pointer seemed to be ... pointing to the wrong place. After some research (and then some help with my research), I came across this post on OBS forums suggesting that this fixes it:

QT_XCB_TABLET_LEGACY_COORDINATES=1 obs

It does, and I never want to do the research for this again, so I'm posting it here and hoping I remember to look here when it happens!