Hey @cata, is there any chance you have a “Nahimic” audio driver? It’s distributed by some OEMs and motherboard manufacturers including MSI, ASRock, ASUS, Dell, and others. This is the thing. It’s possible that you never explicitly installed it and it was put there by something else.
If you can find this thing on your system, try uninstalling it.
There’s a fair amount of evidence on that this driver intercepts some OpenGL functions and causes startup hangs on secondary monitors right in the place where Roon is hanging for you. This is one of the more detailed descriptions but there’s probably 20 github issues in various projects about this hang, and it looks very much not specific to Roon.
EDIT: it looks like ASUS Sonic Suite has similar issues.