When nautilus trashes something, it doesn’t want to have to move it across partitions. This is because it takes a lot longer to move between partitions, and then if you remove the partition then the trash has no place to restore to.
This isn’t a problem on drives which don’t have a seperate home partition because then nautilus isn’t sending the files to a different partition by putting them in ~/.local/share/Trash
Anywhere that is on the same partitions as your home directory is sent to
~/.local/share/Trash. This works across the entire root partition on setups which only have one partition.
On any other partition nautilus will make a
.Trash-1000 folder on the root of the partition, then send all trashed files into that. This works rather well on external drives that you have full read/write access to, though it won’t work if you don’t have write permission to the root of the drive.
/ partition isn’t the same as your
/home partition, and a
.Trash-1000 doesn’t exist with write permission at the root of your system, nautilus will fail to trash files. Thus the delete key won’t work and a trash action won’t be available in the menus.
You could try using a root nautilus and deleting one file so that the
/.Trash-1000 folder is created correctly, then using
sudo chmod -R 777 /.Trash-1000 to give yourself permission to access a trash on the
/ filesystem. I cannot confirm that this will work though you could give it a try, this should be working fine