iOS 14.2 clearly has some serious bugs! We have both an iPad Air and an iPhone 11 Pro showing miserable, unreliable WiFi performance. We have tried many of the usual solutions (e.g. reset network on Apple device, reset router) without success. The most amazing result was when we tried the advice I found to turn on flight mode: nothing happened! The iPad Air shows flight mode enabled, but WLAN and Bluetooth still turned on and WLAN still connected!