Hi,
I've been having issues trying to upgrade an old Raspberry Pi 1B rev 2 to Raspbian Buster (or Raspberry OS).
I bought a WiFi adapter and it worked out of the box with Stretch. I usually use this device in a headless setup so as soon as I rebooted I stopped having access to the pi. Then I tried to flash a SD card with Buster straight from the Raspberry Pi website (the lite version because it's headless) and I had the same outcome (previously I added a wpa_supplicant.conf and added an empty "ssh" file to /boot).
Do you know what's going on? I booted the last SD card with a monitor and I couldn't find any strange errors. I have to say that the adapter is not faulty because I flashed a backup I made of the SD card with Stretch and it's just fine.
Thanks in advance :)