Have you tried accessing the REST API on default port 8080? As far as I know that forwards all requests to gRPC.
That's how I've setup Zaprite for users to access their own nodes.
  • Umbrel uses default port 8080
  • MyNode uses port 10080 (both require https)
It works for Tor and also on clearnet (ex. Voltage) nodes using LND.
But ultimately it could be a docker issue blocking incoming traffic over certain ports.
the library i'm using wants a gRPC socket. however, i did try this for fun to no avail...