If the node can be reached depends solely on your networking. You need to have the lightning port 9735 open and a publicly accessible address.

This is independent of lightning channels.

It's the same with LND or CLN. And you will have this problem on Umbrel if it is not publicly available on a public address.

that's just networking and independent of the app.

If you don't have the node running on the public network you can also open a connection to the channel partner's node first then the other node can open a channel without the public address.