Has one of you done something like this before where you have a mobile 5G modem that is connected to your home net via VPN in a way that puts every device in the 5G modem's local network "into" your home network?

I want to be able to carry self-built gadgets with me that depend on services in my home network (e.g. MQTT), but they are too dump to connect to a VPN themselves, and I don't want to expose any of these services on the Internet.

Most WireGuard docs out there are about a "road warrior" type setup, but I'm looking for more of a "site to site" setup in which the connected local networks are peers.