Sorry, I misunderstood what you are trying to do here. I thought you were trying to use the Atom Echo itself as a media player. Disregard that arduino library comment, it isn’t relevant. I just watched the video since I couldn’t earlier.
Indeed what you are doing should work. Are you certain that the upload was successful? With GPIO21 set as the speaker output, the speaker data should absolutely not work. The fact that it does means that somewhere along the line, the GPIO22 is set as the speaker output.
Yes, but you pretty much have to do a full battery test and pen test like the great Scott video because it is really a 60/40 of getting fake sodium ion batteries from Aliexpress 😅