MS does not provide any possibility to determine all update. The only catalog they provide to the public is wsusscn2.cab, which just contains security-relevant updates.
It is currently not possible to implement the API WSUS uses to determine the updates. But it is possible to download the updates (determined from wsusscn2.cab) from your WSUS instead of MS.
The user Cababs created a list of optional updates not covered by wsusou:
viewtopic.php?f=2&t=4182Using WSUS to determine the updates required to install is technically possible (by modifying .\client\cmd\ListMissingUpdateIds.vbs), but I never worked with WSUS and the VBScript-API. A possible solution may be a similar to the current way, but using "ServerSelection = 1", instead of "3". But I currently don't know, how to feed the WSUS URL to WUA.
Wer Rechtschreibfehler findet, darf sie behalten oder an den Meistbietenden versteigern. / Everybody finding a misspelling is allowed to keep or sell it.
aker
WSUS Offline Update „Community Edition“
https://gitlab.com/wsusoffline/wsusoffline/-/releases