How about VPN to create account? Then later on use Tor to log-in and make post? I did not try but it is my pop-up ideas. I think it can work and maybe better than Tor at beginning.
It's a good idea, maybe OP has to try VPN over Tor. Connecting into VPN first to cover the Tor exit node. Let's do that experiment with free VPN and change all credentials when login success.
https://www.makeuseof.com/tag/can-you-use-tor-and-vpn-together/