This bug is also reported via the UbuntuMATE community:
https://ubuntu-mate.community/t/problems-with-sound-on-rpi-2-3-under-ubuntu-mate/5087
This bug is also reported via the UbuntuMATE community:
https:/ /ubuntu- mate.community/ t/problems- with-sound- on-rpi- 2-3-under- ubuntu- mate/5087