Timeshift needs a partition table - Linux Mint Forums
forums.linuxmint.com › viewtopicMar 04, 2016 · Whether or not the disk had a partition table after formatting it all to ext4 with disks - don't know or if it did, what sort. Do know that going into gparted and creating an msdos partition table worked and like the comments in the link, it left me with less usable space after than I had before (but can't remember by how much).