Hi
I use in my setup a number of mobile devices running VPN clients in a local WIFI.
With OpenVPN it is no problem to stay connected with the VPN "inside" the local WIFI. With Wireguard I do not get any "Handshakes", i.e. it does not work. It works perfectly well from outside the "inside" network of the OPNSense router.
Is there any special setting in the firewall rules to use Wireguard from "inside"? The logging is unfortunately miserable so I have no idea why it does not work.
You could port forward your WireGuard port to localhost, take a look here (https://forum.opnsense.org/index.php?topic=9245.0).
WG works from LAN for me, without any port forwarding, or anything else special that I can think of... the typical default rule to allow from LAN to "any" should cover it, I think.