if you've previously updated from 2004 to 20H2 or 21H1 then you'll know the drill by now. This is a very minor update, installed via a small enablement package that installs like a cumulative update and turns on a few dormant features. There's no big download needed and no Windows.old folder created. Of course, if you are still on 1909 or earlier it will have to update in the traditional way with a windows.old folder.
2004, 20H2 21H1 and 21H2 share the same system files and cumulative updates. The major built number will be increased from 19041/2/3 to 19044 but the minor build number (currently .1348) will remain the same. There are no new known issues reported by MS for 21H2, only those that are already known for 2004/20H2/21H1.
21H2 will be offered as an optional update in 2004/20H2/21H1, but at present you'll only see it if you are a 'seeker' that is 'Microsoft-speak' for anyone who manually clicks on 'check for updates'. And even if you do check, not everyone will see it offered at first. Microsoft say they are starting slowly, and will ramp up to offering it more widely over the coming weeks. Having said that, I've seen it offered on every W10 21H1 machine so far when I've checked for updates.
To be honest, there seems to be very little that's new in this release. As such, there's no real pressing need to take this feature update when it's offered, but neither should there be any reason to fear updating to 21H2.
Starting with Windows 10 21H2 the release schedule for new feature updates has been changed from twice a year to once a year. The next feature update for Windows 10 is expected to be 22H2 in November next year.
https://blogs.windows.com/windowsexperi ... 21-update/Microsoft wrote:We will transition to a new Windows 10 release cadence to align with the Windows 11 cadence, targeting annual feature update releases. We are now renaming the servicing option for releases to the General Availability Channel starting with the November 2021 Update .... The next Windows 10 feature update is slated for the second half of 2022. We will continue to support at least one version of Windows 10 through Oct. 14, 2025. As a second half (H2) of the calendar year release, Home and Pro editions of the November