Please note that this answer is valid and tested on the released version of Ubuntu 20.04 only. As @GavinRay has reported in a separate answer, there are issues with this process on the Ubuntu Community Preview for WSL (currently using 21.04). Please see Gavin's answer for a solution there.
Ubuntu only provides (and tests) LTS releases for direct download and installation on WSL.
You can install the base "Ubuntu" distribution (which is currently 20.04) and then upgrade it to 21.10 with a slight variation on the normal mechanism:
sudo apt update && sudo apt upgrade to make sure the existing release is up-to-date.
sudo apt remove snapd -- Needed because WSL doesn't support Systemd directly
Sudo edit /etc/update-manager/release-upgrades and change the last line to:
prompt=normal
sudo do-release-upgrade to upgrade to Hirsute/21.04
Recommended: Exit WSL, execute wsl --terminate Ubuntu from PowerShell or CMD, and restart WSL/Ubuntu.
Repeat sudo do-release-upgrade to upgrade to Impish/21.10
Recommended: sudo apt purge needrestart to get rid of unnecessary checks after installing any package.
Again, this is not a scenario that Canonical seems to necessarily test, but people have been doing it for a while (as well as installing many other different distributions).
After upgrading, I do recommend creating a backup image. This can be used to create new, clean 21.10 installations in the future if you need to try something out without impacting your normal one.
wsl --export Ubuntu Ubuntu2110_fresh_install.tar
Create new installations from it by creating a directory, and:
wsl --import Ubuntu2110Test <directory> Ubuntu2210_fresh_install.tar
I personally just go ahead and create a new installation automatically. It has the advantage of:
- Letting me name the installation what I want (e.g. 'Ubuntu-21.10`)
- Placing it somewhere other than under
%userprofile%\AppData\Local\Packages
