[wongarsu]

The website doesn't really make it clear, but it supports Windows, MacOS and Linux (in all flavors).

Even though Windows now has a quite good screenshot story out-of-the-box with the Win+Shift+S shortcut, Flameshot seems to have some very nice annotation options that I haven't seen anywhere else.

[nguyenkien]

ShareX is native option in Windows, support screenshot, annotation, record screen as gif or video. And can upload to many services