https://wccftech.com/microsoft-moves-beta-channel-to-its-latest-windows-10-21h1/

Microsoft introduced Windows 10 version 21H1 in February. The company allowed Insiders in the Beta Channel to install this new version but didn't force the version on everyone following the "seeker" experience. That changes today as Windows 10 21H1 is now being offered as a "recommended update" to Insiders in the Beta Channel, the company confirmed through a tweet.

This means that even if you chose not to install version 21H1, you will automatically get it now if you are signed up with the Beta Channel. You can always push the update through Settings > Update & Security > Windows Update > Download and Install 21H1. To confirm, type "winver" in Windows Search to check if you are already running version 21H1.