I’m not sure if I even had iOS 14 installed or not but my camera roll was acting funny so I did the current update 14.1 and all of a sudden I have this same issue with no sound when texts come in and no banners/notifications when locked. I read what another user did and did the same and it fixed it for me too.
I just went to notifications and turned them off, did a hard reboot, turned notifications back on and it works again. I’ve been messing with all day trying to figure it out and thought I had already done this one but apparently not. HTH someone else. Btw...only read to page 3 so this has probably been mentioned already several times. I apologize if it has.