This app was mentioned in 8 comments, with an average of 6.00 upvotes
Headphones is a good one, I use that a lot. Also phone games; robot unicorn attack 2, animal crossing pocket camp, unblock me, and zen koi 2 are big ones for me, gives me something to focus on, pretty absorbing, and effectively distracting. Also if white noise helps, there's the sleep sounds app, it's got a decent handful of nice sounds, some are somewhat customizable.
Getting away from people is hard in some situations but one that works almost everywhere, and that I've yet to have people object to, is me going "Sorry, I gotta run to the bathroom real quick." Bathrooms are good, gives a relatively quiet and isolated space to just take a few minutes, maybe splash water in my face or play with the water from the faucet for a minute (idk why but it calms me down).
Screaming got shifted to humming or singing. If anyone asks, I just tell them "I sing when I'm stressed, it's just a comfort thing." and usually they just nod and move on. No one thinks it's too weird.
Flapping got shifted to clapping. Flapping because you're excited weirds people out. But people seem to be way more accepting of excited clapping, especially if you can add in a little "yay!"
Biting... uh, I never really fixed that one, I just got more appropriate things to bite/chew on lol.
I've just downloaded robot unicorn attack 2 - it's weirdly not at the top.
https://play.google.com/store/apps/details?id=com.pikpok.rua2
It's still a game btw: https://play.google.com/store/apps/details?id=com.pikpok.rua2