Path Check Monior to trigger Failover

As it was mentioned HA Groups are a way to go.

Other than that for monitoring the gateway devices gateway failsafe is also a nice option (there is even a vlan failsafe but as the pool members are not directly connected it will not work):

https://support.f5.com/csp/article/K75303031

Other that an icall script could also monitor the logs and trigger a failover:

https://community.f5.com/t5/technical-articles/what-is-icall/ta-p/288206

F5 has so many ways to do different things it is crazy 🙂 . Do not forget to mark the solution that works for you as accepted if it is found.