Iphone XR can't connect to WiFi

My iPhone xr suddenly wouldn't connecting WiFi that I've been using for over a year and I've tried everything (restarting, shutting down, network reset, disabled location on network, DFU via iTunes) still same error of unable to join network or couldn't find network. I've tried connecting to 3 devices (tethering via two android phones and the home router)

Even when it connects it wouldn't browse or do slowly and suddenly disconnect after a minute or two.

The only way I could install apps back after DFU restore was to share hotspot from Windows and that stayed for hours.

Although disconnected once and connects back after multiple trial.

I'm confident it's a bug and will be happy to try more options to resolve it.

Thank you