iPhone not appearing in Develop menu in Safari

Turns out, my issue was that the update to the latest iOS version disabled the "Web Inspector" settings on my iPhone. To re-enable it, go to Settings > Safari > Advanced.

FWIW, I tried all of these suggestions, and it worked briefly after resetting Privacy & Location settings but stopped working immediately after.

What ended up working as a long term solution was to turn both WiFi and Bluetooth off on the iPhone while connected to the Mac.