Hi @sebjulien
Have you tried [https://www.youtube.com/watch?v=xp6-KJwL0JI|resetting] the speaker and check if that resolves the problem?
If it still doesn't work, looking at this teardown [https://www.youtube.com/watch?v=vw5GSLJsYBY|video] it appears that there may be a separate WiFi/Ethernet board as there's a cable connecting the Ethernet port connector to a board that is then connected to the mainboard. (stop video at 8:52 minutes)
Check what the board number is of that board and search online for that.