Something like this starting happening to me for no apparent reason (no apps installed, no OS update). I tried the usual steps suggested by everyone: resetting the network settings, running safe mode, wiping the cache partition. Nothing worked. I was going to factory reset, when I decided that I should see if there is a way to examine the detailed wifi logs on the device for clues. I followed these instructions to access the log: https://whatsabyte.com/internet/wi-fi-verbose-logging/
As soon as I'd enabled switched on developer mode and enabled verbose wifi logging, the wifi problems mysteriously resolved. I suspect there's something either about entering developer mode, turning on the verbose logging, or connecting to a computer with USB and Android Studio that cleared a value somewhere that was causing the problem. I've now disabled verbose wifi logging and switched developer mode back off, and everything is working fine!
