I discovered that it is not possible to drag a file from inside File Roller into Nautilus when working under Wayland, but it does work under X11. If I’m right, it uses XdndDirectSave. Checking the standard, it seems that it uses a window property, which, AFAIK, is exclusive of X11.
So my question is: if, as I suspect, it is incompatible with Wayland, is there an alternative to XdndDirectSave protocol under Wayland?