I think in that case you should just put your travel router as a user of the group that accesses the home network.

If I set my phone to be a WiFi hotspot with my Netbird VPN on, my tablet can connect to my phone’s hotspot and access my home network even if my tablet doesn’t have the VPN on it.

So in that case I guess the router would be a peer, yeah!

Did you manage to get it working in the end?