I played the 22-11-16 demo that had sound (in the browser on itch.io), and I think I played 30-11 and 09-12 demos (or one of them) that also had sound, but this 23-01-11 no longer has (working) sound. (note I am in Chromium on RPiOS)
PS. Can you also add a second Menu key (specifically for brouser use) like CTRL+M or just M, as ESC takes the game out of fullscreen in the browser - as a desktop app, Esc is quite normal for a menu, but not in a browser, so a second key option would be nice (I thought there was one?)