RASPBERRY PI OS is fine, generally. It’s a 32-bit OS though, and the 64-bit version is a work in progress, with features that don’t work. If you’ve got the 8GB version of the Pi 4, you might be frustrated at only being able to use 4GB of that lovely RAM, but Ubuntu has come to the rescue with a Pi port of 20.10 Groovy Gorilla that’s fully 64-bit, and a great desktop experience.