I've set up OpenVPN and have successfully connected from my remote PC into my Tunnelled network 10.0.1.0/24. My remote device can access the wider WAN through the VPN perfectly.
I can ping the LAN IP address of the OPNSense devices 10.0.0.1 and also 10.0.1.1 from my remote device.
However I cannot ping or reach any other devices on the LAN such as 10.0.0.100 from my remote device.
LAN IP 10.0.0./24
OpenVPN 10.0.1.0/24
I'm sure that I'm missing something fundamental regarding routing between the two subnets but I just don't know where to start.
For routing purposes you need to config "IPv4 Tunnel Network" in VPN server settings with your LAN IP range, e.g. 10.0.0.1/24.
Also make sure the firewall is allowing access from VPN to LAN, e.g. allow source=10.0.1.0/24 dest.=10.0.0.1/24