My biggest concern would be someone scanning CT logs to find hosts with hobbyist grade security. That’s not meant to insult hobbyists, but they might be a juicy target for immediately exploitation after a zero day hits. To be clear, it’s the same for any well known DynDNS domain.

Besides that, I looked at every DynDNS system I could find back in the summer. There were only 3 that I was happy with; Hurricane Electric, Google Domains, and a pair of self hosted Bind servers.

If you want the best, simple solution, and it doesn’t need to be completely free, register a domain with Google domains. If anyone knows of limitations, let me know.

Namecheap maxes out at 150 DynDNS hosts :-(