This is why the concept of running services until different ports than default isn’t a real security measure, it doesn’t actually take any effort to figure out what kind of service is running on a port.

I use a DNS server on my local network, and then I also use Tailscale.

I have my private DNS server configured in tailscale so whether on or off my local network everything uses my DNS server.

This way I don’t have to change any DNS settings no matter where I am and all my domains work properly.

And my phone always has DNS adblocking even on cell data or public Wi-Fi

The other advantage is you can configure the reverse proxy of some services to only accept connections originating from your tailscale network to effectively make them only privately accessible or behave differently when accessed from specific devices

DynDNS

Check out Tailscale.

From outside? Set up a Cloudflare account and point the NS from your registrar to it.

From inside? Set up unbound on a docker host and don’t open it to the internet. Use that one when you’re local and the normal public DNS when you’re outside. But everything I’m seeing in here makes me sure you shouldn’t even consider opening ports in your firewall to expose inside host services. Use a VPN when you’re roaming, and only use your DNS for local servers/hosts via that VPN. The only use for your outside domain name should be to point a single hostname to your outside IP address so you can use it for your VPN endpoint.

Use DNS challenges for LetsEncrypt cert requests and remove host entries from your Cloudflare after you get your cert.

That wouldn’t help with an open resolver.