Since gRPC uses HTTP/2, you may need to specify theDocumentation Index
Fetch the complete documentation index at: https://ngrok.com/docs/llms.txt
Use this file to discover all available pages before exploring further.
app-protocol when forwarding a gRPC endpoint:
ngrok http --app-protocol=http2 80
This works with other ngrok features like custom domains and ports.
This Stack Overflow user also reports that forwarding to gRPC services works using proto: tcp.