[2022] Everyone in Infinite is permanently muted.

This might be a dumb question so apologies in advance but you don't have a child account right?

And have you checked your Xbox account privacy settings to make sure those allow for chatter with others?

Go to your Xbox account settings here and then check "Privacy & online safety" in the bar on the left. (Naturally making sure you're signed in with the account you're playing with.)

Then if you scroll down a little bit there's a setting that's called "You can communicate with voice, text, or invites" and you want to make sure that's set to Everyone.

If you're still not hearing people, I'd hit up Halo Support and see if they have any other suggestions because I'm all out. Good luck!