The first questions to ask would be:

1. Are you using Umbrel to have your own server?
2. Or are you using Umbrel to run a Lightning node?

If you choose 1, go ahead, install all the apps they offer. Including running a browser.

If you choose 2, just use it to run your LN node. Do not install anything else but a few channel management tools. Even though it's supposedly sandboxed, I wouldn't want any externally caused hardware trouble to make me lose funds on my LN node...