I suggest that you focus on your WiFi Router. This includes its location, the number of devices connected, the default channel, 2.4 versus 5 GHz, and so on. TVs, microwaves, and other appliances can cause problems. Google suggestions for the best WiFi experience.
I'm in the same boat, and pretty sure it's something to do with iOS 14.0.1 if you recently updated to it. My phone is essentially a paper weight now -- no cellular signal, wifi calling drops with a call failure after 5 seconds - 1 min max, etc. I have an iPhone X -- my daughter and wife who are still on iOS 13.x and using an iPhone SE and 8 have no issues whatsoever, which is how I was until the day I installed the update.