hello, I want to submit a run to a pretty niche game speedrun, but the only mod has not been online for 9 months and I couldn't get in contact with him in social media, what can I do?

You should submit a Support ticket from Help > New ticket under "Become a moderator for an existing game" https://www.speedrun.com/support/tickets/new

Provide proof that you've tried to contact him and he hasn't responded.

And then once it gets accepted, you'll replace this moderator with yourself and you'll become one

thank you very much