How to access my LAN devices through VPN server?

[bring.fringe18]

You don’t need to manually open ports on the GL device acting as the WG Server; the GL GUI handles that all for you.

I think you should try replicating a far more simplified Client/Server setup before introducing WAN/ISP IPs or LTE. Here, substitute my Certa for a mobile phone running the WireGuard application in the following HOW-TO & this should be as straightforward as it gets:

No TCP for connected VPN clients (just ICMP)

Well there certainly was a hurdle to overcome: after enabling the VPN WG Server GL GUI’s defaults for generating WG Client confs automatically set the endpoint to the public IP. I wanted the WG Client device to connect to the WG Server directly within the LAN, not over the WAN/Internet, so of course I changed that to the WG Server’s IP 192.168.10.1 from the perspective of the Client device. My Client device, the Certa, is known to preform with VPN providers using a MTU of 1320. YMMV. Server …

Then we can make the necessary modifications regarding outside/Internet-side connectivity.