Well if anyone is also interested in getting sound out of their speaker, I finally found two libraries which work, and they seem to be pretty elegantly written (I say two libraries because both of them are needed, it’s not a choice between the two):
Just use the pre-defined board AudioKitEs8388V2 board as an argument when an AudioBoard is called for, for instance in the sine wave playing example. It has the correct pins pre-defined and all.
If you’re using PlatformIO I’d suggest adding both libs to your lib directory as git submodules and to tell PlatformIO to look for them at this to your platformio.ini file:
lib_extra_dirs = lib