If you're looking for a Linux alternative, I've gotten a lot of use of https://flameshot.js.org/ (which I invoke with the print screen key). It "just works" and has a bunch of editing tools close at hand.

Is there a Linux alternative that allows me to film portion of the desktop and do neat little arrow annotations live and everything?

Peek can film portion of the screen but probably can't do annotations https://github.com/phw/peek