1. Yeah, the /nolauncher argument is in there correctly. To be clearer, it was working fine before the 24H2 update. That may be anecdotal evidence, but it's the only correlation I can think of and this behavior is replicated on the three computers I play GC4 on.
2. Yeah, I keep everything updated on my systems.
3. Running GalCiv4.exe directly just opens the Stardock launcher as if I had run it from Steam. None of the other executables in the GC4 folder tree look like they have anything to do with directly launching the game.