lsof comes not preinstalled on my Solus Budgie system. However, it is required as dependency for the Nautilus "Volume is busy" dialog window to work correctly.
I discussed this with the Nautilus developers:
https://bugzilla.gnome.org/show_bug.cgi?id=784830
Please add your view if you think that the problem is different. Otherwise, please add lsof as a dependency for Nautilus.