When it works, it’s so good. But if the firmware got issue, somehow some things just gets broken haha.Apple compatibility with this DAC is something else indeed. I'll let you know when they answer to my inquiry for newer fw.
I managed to get in contact with one of the support people on their Facebook Page messenger. They managed to provide me the factory firmware for the m15i. So now the official Questyle Lightning cable works with my iPhone once again. And the connectivity is as fast as when i just got the m15i the other day. If you need it, i have DM-ed you about it.