I have a Brother color laser printer (technically it’s like LED or something? not home, don’t have the exact model handy). It has built in wifi and ethernet for network printing. The wifi isn’t configured, and the ethernet is manually configured with a static IP for my LAN… but no gateway address. This breaks outgoing network connections to the internet (as evidenced by the printer’s inability to check for firmware updates), while behaving otherwise normally for all my LAN devices. I hope this info is useful!

ZeroTier might suit your use case. It’s super easy to setup.

Maybe see if ‘rclone mount’ solves the problem for ya. Rclone can often be a super handy swiss army knife for stuff like this.