Anyways, dropping in the new usb100.dll gave
12-10-2021 09:59:35 SYS2070 PID 2128 TID 0001 Slot 00a6
H:\TMP\HIDAPI\LIB\HIDTEST.EXE
HIDAPI0->USB100._clock_gettime
127
So I rebuilt hidapi, some wrestling to link to usbcalls (see libcx is also linked in by the pkgconfig script). Things have improved as the PATH error is gone but still unable to open the device.
H:\tmp\hidapi\lib>hidtest.exe
hidapi test/example tool. Compiled with hidapi version 0.11.0, runtime version 0.11.0.
Compile-time version matches runtime version of hidapi.
Device Found
type: 046d c534
path: 1-3:1.0
serial_number: (null)
Manufacturer: Logitech
Product: USB Receiver
Release: 2901
Interface: 0
Usage (page): 0x0 (0x0)
Device Found
type: 046d c534
path: 1-3:1.1
serial_number: (null)
Manufacturer: Logitech
Product: USB Receiver
Release: 2901
Interface: 1
Usage (page): 0x0 (0x0)
Device Found
type: 046d c216
path: 0-4:1.0
serial_number: (null)
Manufacturer: Logitech
Product: Logitech Dual Action
Release: 300
Interface: 0
Usage (page): 0x0 (0x0)
unable to open device
Edit: notice the serial number is still null, perhaps the problem, perhaps caused by working around iconv.