There are many, many out there. I suggest you join one with a deliberately "throw away" account and start following a few people. Then see where they are, and after a time export the list of people you follow, and move.
I'm on https://mathstodon.xyz/ and https://fosstodon.org/ if you want to start on either of those.
Then again, maybe you will neither need nor want to move.
A quick web search for "mastodon instance tech video games" has produces a few pages listing some instances with comments about what sorts of things they cover:
https://thefishcrow.com/2017/04/08/mastodon-instance-content...
Visit one of those pages and Ctrl-F for the things you're interested in. Again, a couple of minutes searching has suggested https://elekk.xyz/about and https://mastodon.gamedev.place/about