I have not updated any DSM yet. I have the old 5.2 there but this is test machine so it does not matter. I just wanted to test the new 1.02b loader.
I followed the instructions exactly as in the first post. Modified the grub.cfg with all the VID/PID, SN and MAC information. I also tried 2 variants, first with keeping the original extra.lzma as comes in 1.02b for ds3615xs synoboot.img and second with replacing the extra.lzma with the one linked in the tutorial. But the result is still the same. The machine boots beyond the point where there is no more info on the screen. But then it cannot be found by the Synology Assistant.
I tried this with all the loaders but the only one which was visible in the Synology Assistant is the 1.01. So possibly I can use this one, but then I can install just the 6.0.2, right?