Hello and thanks for all the effort.
I just wanted to inform you that today with kernel 5.5.0-rc6-sunxi64 I've got sound through hdmi out of my OPi3 for first time ever.
Youtube seems to be working fine out of the box. VLC still doesn't work - system hunged with a mkv file I tried (I didn't have time to check with other files).
That's a huge step forward for me!
Kudos to the developers.