I’m going to put tailscale to the side, as I’m just not sure how to best integrate it here. But for the local network…
There are two pieces to this, DNS and an ingress controller/reverse proxy. The first would ordinarily be managed by your router–you’d need to set app1.mydomain, app2.mydomain, etc. to all point to the IP address of your NAS.
The second piece is a reverse proxy, and the only option currently in the app catalog is Nginx Proxy Manager. Here’s how you’d set that up:
Another option for the reverse proxy is Traefik, but that’s going to be a custom app installation. But it can be configured using labels for the individual apps, which may be a benefit. I like Caddy as a reverse proxy, but it’d once again be a custom app.
This may be relevant about Tailscale: