Microsoft has officially flipped the switch on Windows 10 22H2, it is now available to download in the form of a Cumulative Update through the Release Preview Channel for Windows Insiders, incidentally, that's the only Windows Insider channel available for Windows 10 users as well.
Microsoft did not provide a changelog, mainly because all this update provides is the enablement package to change the version from 21H2 to 22H2. It is a slight bump in build number from KB5015684 (19045.1862), which is publicly available to download from Microsoft and does the same thing, to today's 19045.1865 (KB5015878) Release Preview build.
Yes, you saw correctly, even non Insiders can upgrade to Windows 10 22H2 right now if they want, because all you have to do is download the KB5015684 enablement package, you can view the full details on how to do that here.
Microsoft says that this build is being offered in the "seeker" experience, however being enrolled into the Release Preview Channel means you will get it offered via Windows Update automatically:
this build [is] available to any Windows Insider in the Release Preview Channel via [the] “seeker” experience in Windows Update. This means Insiders currently in the Release Preview Channel can go to Settings and Windows Update and choose to download and install Windows 10, version 22H2 if they want.
You can find the official blog post here.