Download issues should be solved by now. If not, they should be soon.
Jernej, consider returning projects/Allwinner/devices/H6/patches/linux/14-eMMC-workaround.patch to master? This problem was solved only in this way. All this time i build LibreElec manually. Which is somewhat inconvenient.
Nope. It's extremely ugly thing, which halves transfer speed. It was introduced only because I didn't have understanding how to properly write eMMC DT node. Now eMMC works for me on Tanix TX6 box and OrangePi 3 with full speed without issues. If it doesn't work for you, then root cause must be found and fixed.
MusicPi You are on your own with most issues. I don't intend to invest much time in A20, since most peripherals are different than on H3 or newer which I know pretty well. Mostly I just collect interesting patches now and then.
Regarding AP6210, you just need to add proper txt config to brcmfmac_sdio-firmware package. Everything else should be already present.