My request is no longer valid. After additional research, what I was attempting to accomplish isn't possible when using AlbyHub's embedded LDK as your Lightning Node. Why? LDK is intended to be self-contained by design, and does not expose a standard gRPC interface like LND or CLN, required as a Fedimint Gateway (gatewayd), which the Umbrel App Store Fedimint requires to be configured in to function. Ironically, Fedimint has offered an bundeled gatewayd via LDK since v0.6.0, much like AlbyHub. Still, the Umbrel App Store's v0.9.0 doesn't offer gatewayd with LDK. It only offers the Fedimint Guardian itself (fedimintd). I am preparing a feature enhancement request for the Umbrel App Store to follow AlbyHub's model to offer gatewayd install upon Fedimint's initial installation, especially as every other implementation offers both fedimintd and gatewayd. The other option is install CLN or back to LND which I migrated from due to lack of BOLT12 support. And actually, Fedimint is planning migrating from BOLT11 to BOLT12, which is why they began including an integrated LDK as gatewayd several versions ago. I don't want to install a resource intensive CLN or LND just for a Fedimint gateway over a RasPi's, as including the lighter-weight LDK Fedimint gateway in Umbrel would be much more efficient usage of the system's precious resources.

Thank you both for your helpful information gentlemen. However, I may have found what I was looking for: "umbrel@umbrel:~/umbrel/tor/data/app-albyhub$ sudo nano hostname" via SSH in UmbrelOS contains a .onion address to my local Alby Hub instance that successfully loads in a Tor browser. Please let me know if I am conflating the issue and the onion address I found isn't what Fedimint is asking for.

LDK tor support is still in the works -> https://github.com/lightningdevkit/ldk-node/issues/178

Public and Tor addresses for the node need better visibility and configurability. It's okay to hide things and set defaults for new users, but there should be an "advanced mode" available where these settings are exposed and users can configure them as needed.