Ubuntu – Nautilus trash doesn’t show deleted files on other partitions

GNOME is using .Trash correctly as far as I understand - if you look in gio/glocalfile.c source you'd see that it does make an attempt to use the .Trash directory if it exists. Do note though that the directory has to have the correct permissions for users to be able to safely store trash files in it (and in safely here, I mean that other users won't be able to recover user's trashed files). For this GNOME requires that the .Trash directory must have the sticky bit set on it - see Trash Directories,note (1) in FreeDesktop.Org's Trash specification.

The main problem with the above approach, is that most r/w removable media you find is FAT, which doesn't support the sticky bit so the only way to handle this safely is to use a per user trash directory.

Regarding root Trash - I can't reproduce the problem you describe, it seems to work well for me.

Regarding /etc/fstab - I'm not sure what is the problem there: you should need to mess around with fstab, unless you want full control over where an external file system is mounted. Normally removable media is mounted automatically upon detection in /media for the user that is currently active, but it is then inaccessible to any other user. If you want a different setup then you should mess with the configuration file. I don't see how that relates to trash, though.

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.

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.

Because your / 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.