Note that you don't need a marketed-as-"dynamic DNS" provider to have dynamic DNS. You just need a DNS provider with an API. Cloudflare has a DNS API. So if yo

Note that you don't need a marketed-as-"dynamic DNS" provider to have dynamic DNS. You just need a DNS provider with an API. Cloudflare has a DNS API. So if you search "Cloudflare DDNS" you'll find five or six different Github projects (some binaries, some scripts) you can run on any box in your house (maybe a Pi?) that'll do your DDNS through them. (You don't need your router to run a DDNS client, even though routers make it seem like a router-exclusive feature. The only thing your router knows that your LAN doesn't is your network's external IP address. But a DDNS client can just hit an external reflector endpoint for that.)