From what I’ve read on it. Umbrel does not yet support https. If you are curious there is a post on this forum that touches on it. I wont go into it here as I did in the other post but it would be beyond useful if the devs got this figured out as in my opinion Umbrel could not possibly leave beta until this is done as alot of the apps are functionally broken (ie. Nextcloud, Vaultwarden, etc.)
Here is the discussion about https on Umbrel:
How can I turn on https?