I just bought Steinberg Absolute 6 a short while ago and installed The Grand 3 on one of my PCs (Windows 11, latest version).
I’ve had issues with The Grand 3 in REAPER 7.07 (did not test on my other DAW, Digital Performer 11.3) like REAPER project not retaining saved status (always warning that the project was modified despite multiple saves in a row without anything else being touched) and the MIDI clip playing back a sequence with The Grand 3 loaded not able to perform undos.
I did a test where I used the very same REAPER project but replaced The Grand 3 with another of my VSTis (Korg TRITON Extreme VSTi3) and everything behaved normally.
Now maybe it’s a performance issue. The Grand 3 is my first “proper” big piano library and maybe I need to adjust some things. The PC used has intel i5 eight generation and 12 GB RAM.