Does the latest Windows Server Cumulative and Quality Monthly update cover patches back to 2019?

That's correct, windows monthly roll-ups are cumulative.

Rather than receiving several updates each month and trying to figure out which the organization needs, which ultimately causes platform fragmentation, administrators see one cumulative monthly update that supersedes the previous month’s update, containing both security and non-security fixes. This approach makes updating simpler and ensures that devices are more closely aligned with the testing done at Microsoft, reducing unexpected issues resulting from updates.
https://learn.microsoft.com/en-us/windows/deployment/update/waas-overview#quality-updates

The latest SSU plus monthly rollup are all that's required.

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Hey @troy price

In my experience. yes and no.
let me explain.

for Yes.

• Cumulative packages, have inside, several paths, which yes, contain past security paths, critical etc. unusual a server will request a package from a very old year, since this missing update will already be considered "superseed" by a new version...so an accumulative package of 2023 already includes all the necessary packages.

for exemple: this is a package from 03-2021

and this is a list of new packages that already include these fixes.

so...it is not necessary to install the 2021 package.

The WSUS server will inform about this. (superseed paths)

However...there are specific cases, for very outdated servers, where the installation of an accumulative package from another year is requested. the same could be due to the installation of resources like .netframework which have several security packages available as well. recently, I came across this scenario, where the 2018, 2021, and January-2023 packages were requested.

• My tip is to use the wsus automatic approval feature, for critical and security packages and perform a "cleanup in database" for superseed paths

hope this is help you.

regards