VPN Cascading doesn't appear to be working properly on Flint 2

It could only help. I’d then set up WG for the LAN as a test before compounding on VPN Cascading. See attached; you could probably skip the MTU aspect.

Do note most VPN Providers don’t allow incoming/port forwarding when active. Proton VPN is an exception but it requires addn’l software on the router to do so.