It is possible to do it with the Umbrel LNbits docker container, but is a lot of work, using nginx. Also every time Umbrel is updated those settings will be wiped.

I would suggest to use a separate machine for your LNBits. It could be any simple PC with a LinuxOS.

Just install LNbits on it, configure its .env file to point to your local Umbrel machine, as funding source from your LN node, using the local IP of your LN node and port.

Then just configure the LNbits with Caddy (see the Lnbits instructions for that) that will take care of your https certificate and access. Is very easy.

Here I wrote a guide about multiple ways to run LNbits https://darthcoin.substack.com/p/build-your-own-lnbits-app-server

Here is the instructions manual to install and configure LNbits on a Linux machine https://github.com/lnbits/lnbits/wiki/LNbits-Documentation