I have a PFSense instance with a gateway group and failover on link down. See this for details: https://docs.netgate.com/pfsense/en/latest/multiwan/concepts.html

It sounds like that's the easiest way to get "high availability" on WAN, is that right? I've also head of "SD-WAN" such as speedify. Does anyone have experience configuring a central router to tunnel all traffic through two WANs using that?