Apple’s iOS 14 has only been official for two days now and the first somewhat major bug was discovered. One of the cooler features of the new build is that you can finally pick your own default browser and email app. However it turns out each reboot will wipe those preferences and restore the Apple apps as default.
This means every time your phone battery dies or you perform a restart you’ll be once again directed to using Safari and the Apple Mail app until you go into settings to change to any alternative browser and email client.
This issue will likely be patched as soon as the next build of iOS 14 comes through but, for the time being, you’re stuck with having to reassign your defaults each time after a reboot.