I've exhausted all new 3.10.1 combinations (see below).
All have a clean, complete card1/eld#3.0 now but NONE has HDMI SOUND.

1.  hdmi-1 + hdminva3-patch
2.  hdmi-1 + hdmi-2 + hdminva3-patch
3.  hdmi-1 + hdmi-2
4.  hdmi-1

Please note that I repeatedly checked if there still was HDMI SOUND on 3.7.0
(on the possibility that, say, the cat ate the cable in the interim - I don't
have a cat, BTW :).

There must still be something, somewhere missing from the original, good 3.7.0
logic.