Selfhosted

Given your setup, I presume you're trying to access your server via a domain name, only from within your home network? That's what the linked blog posts are talking about.

EDIT: It seems several are confused by my use of internal IP addresses in this way, yes it is entirely possible. There are multiple people reporting to use exactly this kind of setup, here are some examples.

Or maybe your example IP address is just confusing. IP addresses in the ranges 192.168.0.0/16, 172.16.0.0/12, and 10.0.0.0/8 are all reserved for "private routing" and are not routable on the larger internet.Your home will have devices with those IP addresses because it's a private LAN that uses Network Address Translation (NAT) at the boundary with your ISP. Your ISP might also have it's own NAT called Carrier-Grade NAT (CGNAT) that has another translation boundary where it reaches the internet. If your ISP doesn't have CGNAT, and allows incoming connections on your desired ports, you might be able to use the IP address your ISP assigned your router as the pubic IP, but if not you'll need to figure out some other routing method (e.g. VPS hosting a private VPN exit point with routing rules to allow incoming and entry point somewhere in your network with routing rules to reply thru that VPN).

EDIT: Added quote

Your issue is using a non-routable IP on a public DNS provider, some home routers will assume it's a miss configuration and drop it.

If your only going to use the domain over a VPN and local network, I would use something like pihole to do the DNS.

If you want access from the internet at large, you will need your public IP in your DNS provider.

It's very likely that DNS servers aren't going to propagate that A name record because of it being an internal IP. What DNS settings are you using for Tailscale? You could also check that the address is resolving locally with the command host mydomain.tld which should return mydomain.tld has address 192.168.10.20 if things are set up correctly.

Edit: you can also do a reverse lookup with host 192.168.10.20 which should spit out 20.10.168.192.in-addr.arpa domain name pointer mydomain.tld.

One thing you probably forgot to check is if your TLD registrar supports DyDNS and you have it set on both sides of the route.

Do a curl http://mydomain.tld/ -i with your server off/while off-network.

Your registrar probably has a service to rewrite http accesses to https automatically. Curl -i shows the headers, which will probably confirm that you're being redirected without even connecting to anything in your network.

Sorry this will most definitely not work with your local IP address on an external DNS. That is not routable over the internet. I have a 192.168.10.20 IP address in my home network as well. You need to go to whatsmyip.com or ipchicken.com and get your external IP and put that in the DNS at your registrar. Most likely you will need a Dynamic DNS provider as your ISP probably gives you a dynamic public IP address that will change occasionally.

If you just want to resolve mydomain.tld INTERNALLY so you can use a mydomain.tld HTTPs certificate then you just need to add mydomain.tld to your INTERNAL DNS server pointing at your INTERNAL IP address for your server. Likely your router is set up as a DNS server but it just forward all requests to the external DNS which is why you just get sent to mydomain.tld instead of your internal server.

Have you considered using a mesh VPN instead of opening a port to the public? Nebula and TailScale are both great options that have a free tier which is more than enough for most home use cases. With Nebula you can even selfhost your discovery node so nothing is cloud-based, but then you're back to opening firewall ports again.

Anyway, its going to be more secure than even a properly configured reverse proxy setup and way less hassle.

Without posting your config we can't really do much.

I have a similar setup with Traefik getting a cert for a public domain for my private server but didn't have any issues.

The IP address you've used as an example would not work. That is a 'local' address, ie home address. If you want DNS to resolve your public domain name to your home server, you need to set the A record to your 'public' IP address, ie the external address of your modem/router. Find this by going to whatismyip.com or something similar.

That will connect your domain name with your router. You then set up port forwarding on the router to pass requests to the server.

You can't point to 192.168.X.X that's your local network IP address. You need to point to your public IP address which you can find by just searching 'what is my IP'. Note that you can't be behind CGNAT for this, and either need a static IP or dynamic DNS configuration. Be aware of the risks involved exposing your home server to the internet in this manner.