So, I installed Houdini (Win 11 Pro) using the launcher. When I go to startmenu, show all apps, under SideFX software 'folder', I only see launcher and Houdini. I must be missing something silly.
It is, though I'm not sure why it's no longer in the Start menu. You can still launch it via Render > Mplay > Load Disk Files or via the commandline (mplay.exe).