Raspberry Pi OS is a well-supported Debian derivative but there are a wide variety of operating systems available for the Pi. I don't run Raspberry Pi OS on any

Raspberry Pi OS is a well-supported Debian derivative but there are a wide variety of operating systems available for the Pi. I don't run Raspberry Pi OS on any of my Pi's. That being said, I do run a Debian derivative on a few of my Pi's, Ubuntu server. I run OpenWRT on 2 Pi's and Fedora Desktop on another.