Allow wired client access to WAN but block access to LAN
I recently had to provide an internet connection to my PV Solar Panel system inverter (SolarEdge brand) to allow system monitoring. It had previously used a 2G cellular data connection through T-Mobile, but with T-Mobile shutting down its 2G network, the inverter needed a different internet connection. The inverter has an ethernet port, so the simplest solution was to use an ethernet patch cord between the inverter and my Archer C9 router.
The inverter only needs the internet connection to allow my PV system's performance to be monitored via a website and app. There is no need for the inverter to communicate with or have access to any other clients on my home network.
Is there a way to allow a client hard wired to my router access to the WAN while blocking access to my LAN?