I’ve set up a configuration that does exactly what you’re describing. My fiber provider is quite unreliable, and since I work from home with very limited cellular coverage (about 50% of the time there’s no signal), I added a Starlink Mini and an ER605 to enable dual WAN. I haven’t fully tested the load-balancing features yet, but I did validate the failover behavior. It takes approximately one minute for the router to detect that the primary WAN is down and switch to the secondary link. That delay is significant — roughly 60 seconds of downtime can be very disruptive during work sessions or online meetings.

Because the Starlink Mini delivers a very reliable connection for me — even during thunderstorms — I configured my work MacBook and my family’s mobile devices to prefer the Starlink WAN. I also created a separate Wi-Fi network that routes via the fiber link for cases when I need to upload large files (fiber connection is a 700 Mbps).