When switching to Windows 11, I encountered the problem that I was unable to do anything involving drag & drop of plugins (including rearranging them and sometimes even opening a GUI window for a plugin especially on master bus). The problem was “visible” by a slightly different mouse cursor after grabbing a plugin: instead of the rightangle thing with and arrow I only got the rightangle thing.
Workaround: It turns out, the Ardour does not seem to interact well with NVIDIA gaming overlay, which is switched on by default. Switching off NVIDIA overlay in NVIDIA app settings fixed things.