My mum taught me the ear popping thing, while we were traveling by air, to relieve the ear pressure.

I can do it on command but never paid attention to how before.

It's basically "yawning manually". There's a couple different muscles activating at the same time, most irrelevant to the popping, I can't control them individually yet. (Probably learnable, if I practiced I could probably get the pop more efficiently.)

But yeah, just yawn real wide, that should do it.

A lot of stuff is learnable, like I couldn't move my ears but taught myself how to do it because I was bored.

I'm not a diver but I suspect it can be learned. I have allergy issues that cause my ears to not equalize when allergies are hitting and I think I just learned how to do this. its just sort of muscle that can sort of be lightly controlled. Controlling one side vs the other I can't really manage.