I don't twitter or mastodon. But isn't "people who share your interests and then connect with them" exactly what the different mastodon instances are for? You're kinda supposed to find a server that aligns with your interest.
You can usually browse an instance without having an account, for example: https://mastodon.gamedev.place/explore (user directory) https://mastodon.gamedev.place/public (stream)
And once your instance federates with it (happens automatically, just needs any user to follow any user on the other one), you can search for hashtags.