Answering my own question, this did the trick for me:
this.input.addDownCallback(function() {
if (game.sound.context.state === 'suspended') {
game.sound.context.resume();
}
});
Before y’all think I didn’t bother to read the documentation or even the warning given, I had that exact code bound to “pointerdown” and/or “pointerup” - but apparently that doesn’t cut it. Crossposting the same answer as on the other thread as this one may be slightly more, er, googleable?