While IDK exactly but presuming it is related to Windows Enterprise or Server Edition OS. Correct me if I'm wrong. And about the 2nd question, if serverrdsh means what I just said, then no. I generally install/use Windows Pro.
Strange. I gave the .1 installer another try on my laptop after installing the latest AMD driver packages (both GPU and chipset) + the Samsung NVMe driver (but that was old on the desktop machine as well during the successful upgrade) and WU found some other "HP software component" inf "drivers" (not real devices and there is a bunch of these) + I weeded out some obsolete driver packages with DriverStoreExplorer. And the upgrade succeeded this time (it's already on .21 by WU and went through a few reboots since then). I suspect the AMD GPU driver was the fault because the fresh package failed to install without the "Factory Reset" option ticked (aka "clean install": uninstall, reboot and then install instead of simple update).
19041.1 was released to Insiders on 10 Dec. 2019. Since then, there has been 1 CU released 19041.21. There have been NO newer Builds like say 19042, 19043 etc. released. So looks like 19041.1 is it. Also remember Microsoft said they would release 2 versions 20H1 & 20H2 in 2020, so 20H1 could not be released in Dec. 2019 even if it is done.