Not connecting to wifi

Yes, but NO other data is involved. See this paragraph:

Go to Settings > General > Reset > Reset Network Settings. This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you've used before.

Extracted from:--> If you see No Service or Searching on your iPhone or iPad - Apple Support

Regards

Giulio

Comment: Not sure that keychain can save your wifi passwords. I use a simple method: before doing any reset/restore/update I create an encrypted backup of my device using iTunes on my computer, and then restore data from that backup.

Question: No idea about that, also because you didn't explain how that's happening. What happens when you try? only at home? with all wifi networks? did you get an error message?

Regards

Giulio

Try this workaround:

Disconnect all the devices from your home wifi modem-router.

Turn ther router down for at least 5 minutes, then turn it back on, waiting for its complete auto-config.

Reconnect your device.

Regards

Giulio