Not sure which ports are required for your usage but maybe cloudflared would work? It works on the free tier as well, you can install cloudflared on your linux/windows server (no BSD support afaik).

Freenom’s domains are pretty unstable, they lost management for .ga domains last year and they often claim others’ free domain when they have high usage.

though if you have unstable network I won’t suggest self hosting fediverse stuff.