I use a cheap Mikrotik LTE Router as a second route. It has the smallest data plan my provider offers - but it’s enough for maintenance and if I need more due to the main line being faulty it’s the same provider’s fault and they pay the bill anyway.

It mainly goes into the OPNsense as a second gateway,but it also allows me to VPN in and reboot the OPN if needed.

If the OPN would be fucked totally in theory I could run the network directly over it,but that would be nasty.