I have successfully updated my device to firmware 1.30, thank you so very much for your support and for offering the latest firmware!
(Perhaps,
@Joe Bloggs might be able to enlighten me on why it kept failing to update via OTA?)
I've also performed a full factory reset, afterwards, to be sure. Now the device appears to function as expected.
After the factory reset, it defaults to volume 40 and Amplifier Type: AB. Gain Low.
Under these settings, I've plugged in my Meze 109 Pro and I could hear normally, even though it wasn't loud enough for me, so I raised the volume to 50.
I've switched to Class A, to start burning it in. Should I give it like 200 hours or less, maybe?
I won't judge the sound quality until then.