I had a problem with my FIOS internet a couple days ago that required a Verizon technician to resolve on the utility pole down the road. Used my AT&T iPhone 12 ProMax as a hotspot over wifi with my 2018 Mini for about 5 hours in the meantime. Worked perfectly, no disconnects even when the phone went to lock screen. And I'm in a rural area which typically only gets a 2-bar cell signal inside the house. iPhone still on iOS 16 and the Mini is on Monterey, so maybe that has something to do with it?