I've been going crazy over the past couple of days because my WiFi stopped working after updating to iOS 14. I have 2 iPhones (iOS 14.5 beta 5) and both of them have an unusable WiFi while my laptop's WiFi works just fine.
So last night I found a temporary fix. What I did was connect my laptop to our WiFi and opened the hotspot then shared the internet connection using a option in the settings, and then I connected my iPhone to my laptop's hotspot using WiFi. Only downside is you have to keep your pc running for the whole day but it works! I tested it on both phones and it works just fine. Apple obviously still have to fix this but I was happy I can use WiFi again.