Proof of work (via one time payment) is an established way to prevent abuse. If you wanted to keep it “free” you could hold it in a pseudo-escrow account. You keep if the account spams but you return if a good faith user wants to close their free account. To my understanding Some no-KYC exchanges do something similar to incentivize the two unknown parties to act honestly. That’s fairly complex but an option.

I finally got into my free account but Unfortunately I can’t get it to upload anything on mobile. It doesn’t seem to load all the way.