The 3.5mm jack on Screenly Player Max plays sound
Selecting the 3.5mm jack as the audio output on a Screenly Player Max now sends sound to it, instead of to HDMI.
Setting "Audio output" to the 3.5mm jack under Screens > a screen > Settings did nothing on a Screenly Player Max. The sound kept going out over HDMI, and anything plugged into the jack stayed silent.
It works now. A Player Max wired into ceiling speakers or a soundbar sends its sound there.