Running Ubuntu on your Raspberry Pi is easy. Just pick the OS image you want, flash it onto a microSD card, load it onto your Pi and away you go.
64-bit. Works on: Raspberry Pi 4, Raspberry Pi 400, Raspberry Pi 400.
https://ubuntu.com/download/raspberry-pi
SHA256SUM: 5187d507099f26bc4d8218085109af498fae5ff93b40c668f83bab5c7574d954 *ubuntu-21.10-preinstalled-desktop-arm64+raspi.img.xz"