Basically allowing multiple users logged into Windows at the same time boils down to modifying 12 dwords (32-bit words) or 48 bytes in termsrv.dll and the content and location (byte offset) varies depending on which version it is.

The rest is just fighting with file lock behavior, Windows self-repair, updates, anti-virus and things that tries to ‘correct’ the modified file so the changes stick. These are hell of hard and tedious.

RDP wrapper was the tool to do this but it stopped updating since 2017 so it won’t track any updates and newer versions pushed later.

There is a tool called autoupdate that rides on top of RDP wrapper which automates the process for each version that was pushed out with the (byte location, byte values) defined in a config file called rdpwrap.ini.

Basically extract all the zip files to the same folder and copy the latest INI file along with it, run the helper routine

autoupdate -taskadd

to add the startup hook (running helper\autoupdate__enable_autorun_on_startup.bat does the same thing) then run the main routine

autoupdate

That’s it!