Whenever I lose a game, I always force myself to analyze it. It might seem hard at first but it really does help.
How to manage loss rage?

The number one way is probably don't show your anger in the chat its not needed, also it's a pretty good way to not get banned.

cuss out your opponent?
Pretty much do the opposite of that, anger is only going to make things worst in the long run.

i knew a guy that would do 10 pushups after every missed free throw... 🤔
Ouch, that would hurt the arms! Think I know why he's missing his free throws

Smash your ego and grow up. It's a big world out there and you are just a drop in the ocean, not the king of the world. You may and will lose, get use to it.
Practically you can take a break and do other things for a while. You can practise this mantra if it helps "People do mistakes all the time, and I'm no exception"
No, no, no
I am just the ocean in a drop ;o)
I remember one game I played I thought for 45 minutes on one move and was unable to figure out the position and lost because of it. Later I hooked up my laptop to my TV and analyzed the game. My old German buddy Fritz(the engine) immediately spotted the tactic I missed which would have given me a strong attack and I was like "Dang it! I knew something was there. I knew it! I knew it!" and threw something soft at the tv.....It may have been a pillow or perhaps a stuffed animal of some sort. I wouldn't call it rage though....it was more like frustration and was short lived.