Porkbun is a registrar that also has DNS hosting, and ACME DNS challenges just need DNS hosting. I also use Porkbun and I am happy with them as a registrar, but their DNS service wasn’t working out for me and I host my DNS records on Desec. It’s working well for me after I increased some timeouts in my ACME client configuration but I can’t recommend it if you’re having problems with Porkbun because the Desec rate limits are strict and their TTLs are high and if you don’t already know what you’re doing you’re likely to spend a lot of time waiting for propagation or rate limits.