(It's an Asus RT-AX86U Pro - so fairly chunky in terms of spec)

I have your exact router make and model! I self host my own server with a domain on my home network and make use of the built in DDNS feature.

My domain registrar is Cloudflare so I have to use a custom script for DDNS, if you’re in the same boat I can provide the script.

I would suggest looking into Asus WRT Merlin Firmware, the custom firmware enables more functionality to your router.

Docker containers for

1. Ghost
2. Nginx Proxy Manager

When hosting a reverse proxy like Nginx, Traefik, SWAG, Pangolin, etc keep in mind you 80:80 and 443:443 ports need to be exposed to the host machine then you will forward those ports on your router. This will allow your reverse proxy to communicate with Lets Encrypt generating and verifying your SSL certificates.

That would be a good place to start. Which providers does it support?

Running a service like ddclient may give you more options at the cost of being more complicated.