TPDD client:flopy2
The Tandy Portable Disk Drive 2 came with a "dos" called "flopy2", on the utility disk.
The only way to install it is to bootstrap using the utility disk that came with the drive.
You can't make a copy of the disk from a download, nor with a normal floppy drive, not even and old 720K drive, even though the TPDD uses normal 720K (NOT 1.44M!) 3.5" disks.
You need the original utility disk, or a physical copy that was made in a real TPDD drive using the backup utility from the utility disk.
Some copies are for sale here:
https://www.arcadeshopper.com/wp/?page_id=11#!/TPDD2-disk-26-3814/p/141211028/category=28313042