I used
EFS Professional to get into DIAG mode, installed
this driver, the com port used varies a bit from the one described at
the instructions (showed only a few, so it was not hard to see which one was the right one, you can try a "trial and error"), and when modifying the NV I did not select all the GSM - WCDMA Bands like the author did, since selecting Japan 1700 and XI - 1500 would cause it to show no signal at all.
If you try it, please make sure to annotate somewhere your #1877 code so I can compare it with mine (pm it to me if you want to, although all 906 should be the same (since its bands, not imei or anything personal) I think I did not memorized it correctly, just to double check).
BTW, when entering into service mode (code 2263) via Shortcut master (free on play store) and comparing it to my Note 3 int. I can select all the same bands except one, the Note 3 has Band 20 whereas the G906S has Band 17, So I am guessing it does work? (need more objective testing though)