The snapshots packages are intended for use with MRPI only, which is why they cover every FW 2.x & FW 3.x devices in a single package, as @knc1 explained. (And while MRPI will honor OTA bracketing, it's irrelevant here since it's [0...MAX]

).
The binaries in the FBInk thread are all you probably need (you'll want the K3 one). As I said, it's standalone. USBNetwork basically just adds a symlink in $PATH.
----
Random remark @knc1: --info implies --keep

. (I also very recently fixed some stupid behavior around --unwrap that was deleting the input in certain failure codepaths, so I definitely get the idea behind 'let's throw --keep in there just be safe' ;p).