iPhone 16 pro wifi connectivity

Your iPhone 16 Pro likely drops the main high-speed Wi-Fi because of a conflict with SON (Self-Organizing Network) band-steering or Apple's Private Wi-Fi Address feature clashing with the router's IP assignment. Since the IoT network (usually locked to 2.4 GHz) works, your phone handles the single fixed band better than the main multi-band network. 

Try this

Turn off Private Wi-Fi Address for Home Wi-Fi: Go to Settings > Wi-Fi, tap the "i" icon next to your main network, and turn Private Wi-Fi Address Off. 

Disable Wi-Fi Assist: Go to Settings > Cellular (or Mobile Service), scroll to the bottom, and turn Wi-Fi Assist Off so it stops trying to drop the signal.

Forget and Rejoin: In Settings > Wi-Fi, tap the "i" icon next to your main network, select Forget This Network, then reconnect with your password.

Reset Network Settings: Go to Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings (Note: This clears saved Wi-Fi passwords).

claiborama wrote:

I've tried all these things and it still drops home wifi. so infuriating.

Just create a 5Ghz only WiFi network on your router and connect your devices to that one. You don't want to be using the 2.4Ghz band at all. It is only included now for backwards compatibility with older devices and suffers from interference and limited channel bandwidth problems.

I've tried all these things and it still drops home wifi. so infuriating.