I’ve just release subiquity 21.04.2 (which was the version of subiquity included on the 21.04 installer) to stable.
Due to a bug that causes a crash when the snap is refreshed in the version of subiquity on the 20.04.2 installer, the new version is not yet offered to users of 20.04.2 but users of 18.04 and older 20.04 installers will be offered the new version. I’d be interested to hear whether people thing having the new version be available is better than having a clunky experience on upgrade.
As usual more details are on github: https://github.com/canonical/subiquity/releases. 21.04.1 was never released to stable so read its release notes too!