@the_gayest_doggo steam's in nonfree repo. Discord updates itself even in the targz version (except for some updates, but they don't happen very often even on canary), but there's a tool called dvm written by my friend which makes updating a breeze. Also it runs in a web browser. You can get an AppImage for nextcloud, but I'm not sure if it auto updates since I don't use it. Riot runs in your web browser.
Not sure about Psi and openarena.