These dfu files are various firmware upgrades for the original nanovna.

Some allow two or four traces to be visible at any one time, others may try to
extend the frequency range (but with reduced performance above 900Mhz.

Others add a battery icon (requires hardware mods) or have the odd extra terminal
command added.

In general, if you have a working unit, leave it alone !

But if you want to experiment / take risks then that's up to you.

-----------------

Using DFU-UTIL command line..

Hello Andy,

When you look what is online on USB you will see (nanoVNA):
$ dfu-util -l
...
Found DFU: [0483:df11] ver=2200, devnum=16, cfg=1, intf=0, path="20-1", alt=1,
name="@Option Bytes  /0x1FFFF800/01*016 e", serial="FFFFFFFEFFFF"

Found DFU: [0483:df11] ver=2200, devnum=16, cfg=1, intf=0, path="20-1", alt=0,
 name="@Internal Flash  /0x08000000/064*0002Kg", serial="FFFFFFFEFFFF"

When flashing, you have to select alt=0, and USB ID 0483:df11.
e.g.
$ dfu-util -v -d 0483:df11 --alt 0 -D NanoVNA_with_scan_and_1500MHz_tinhead.dfu

This worked on MacOS, but I am shure it will also work on Linux.

73, Rudi DL5FA