and when dwm.exe is doing those things, despite you asking it not to via disabling fullscreen optimisations? Is there anyone here who runs games in exclusive fullscreen mode, with all v-sync disabled, by forcing 'disable fullscreen optimizations' to on for the game's executable via its properties? And can tell the difference between the framerate actually being unlocked, the fullscreen mode actually being exclusive without interference from dwm.exe to try and make overlays (such as the Win10 volume one when you use a keyboard button to change it) cover the game window anyway, or attempt to make screen tearing less bad or whatever else it is that it does. I'll most likely keep running LTSC 2019 on old hardware and install LTSC 2021 on new hardware. Though the manufacturer's driver package could sort it out, it's kinda unexpected for a new release on old hardware. It's also weird that LTSC 2021 fails to find drivers for 3 chipset devices on my Z390 motherboard, which isn't an issue for LTSC 2019.

It looks like Microsoft has given up maintaning backward compatibility as their main focus now is Windows 11. I haven't tried more stuff yet, such like PS CS6, but I assume LTSC 2021 is just Windows 11 compatibility disguised under a skin of Windows 10. PowerCalc XP gets warned about compatibility/security issues. VMware Workstation 12.5.9 causes the 21H2 host to BSOD. My reason to switch back to LTSC 2019 for now is because LTSC 2021 breaks compatibility for some legacy old stuff: I've noticed some minor improvements in LTSC 2021, such like Task Manager offering the option to remember which tab to start with, or showing GPU temperature etc (I've skipped all semi-annual releases so some of these changes occurred pre 21H2). It has cost me 8 hours for YOLO with LTSC 2021 without cloning my old installation of LTSC 2019 first. Despite me being pretty active trying LTSC 2021 on my main physical desktop, I've re-installed back to LTSC 2019 for now.

Windows 10 enterprise ltsc 2019