This is still a bug, see:
$ gio trash foogio: file:///home/user/test/foo: Trashing on system internal mounts is not supported
In order to reproduce this bug I did the following 1) create a partition and format it to ext4 2) mount that partition to /mnt/test 3) bind 'test' to /home/user using fstab 4) 'touch foo' 5) gio trash foo Debian GNU/Linux bookworm/sid linux 6.1.0-3-amd64 Xfce 4.18 gvfs 1.50.3-1