This for example is a full description:
"Analog and digital audio support - Includes stereo headphone out and microphone in analog ports and S/PDIF digital output port."
https://support.lenovo.com/lv/en/accessories/pd011741
On the Boox page there is the pictogram of the earphones, but it is not clear what it means.
At the bottom of the page "Poke 3 vs Poke 2"
https://www.boox.com/poke3/