This is fair, and does solve the problem. I didn’t explicitly state that I needed it to be convenient, so you’re right. Having one network that is LAN only and switching to it to use Jellyfin, and having a second network that is WAN only and using ProtonVPN there would probably be the most secure setup. Unfortunately, it still doesn’t solve the issue of encryption in transit over the LAN, but that might be fixable with Tailscale. The LAN could even be ethernet-only, to mitigate wireless attacks.

That makes me wonder if there’s a way I could simply plug an ethernet cord from my phone to the airgapped Pi and use it that way. Is that possible? Surely it is. Could ProtonVPN be used on the phone even while the phone is connected physically to the Pi?