Looking for a modem/router with failsafe threshold

Can't find any information about this, so hopefully someone with some information about it will help me out i am looking at getting a router that has 4G back up failsafe that i can set the threshold for 

e.g starlink upload starts to drop bellow 5mbps so the 4G failsafe will kick in until it goes back up past 5mbps 

if someone could let me know what routers/modems have this feature please let me know!