Is it possible to save a backup of sorts of a wireguard connection, that will kick in when the other one fails to make a handshake for an x amount of time?
I notice the vpn that i use sometimes has maintenance that makes me unable to connect, but a other location would then work. Thats of course not ideal for a router, as the internet in the house then fails to work...
Take a look at watchcat -- this can be used to detect the state of a connection. From there, you can kick off a script to shutdown the interface that has stopped functioning, and then bring up the backup interface.
You may also want to consider using mwan3 which can actually manage the failover (instead of watchcat).
I believe mwan3 has a luci package. I would have to look for watchcat.
EDIT: Both have luci apps associated with them.
luci-app-watchcat - git-22.210.22699-010119f - LuCI Support for Watchcat
luci-app-mwan3 - git-21.340.50573-2af8158 - LuCI support for the MWAN3 MultiWAN Manager