Ubuntu 22.04 comes with the snap version of Firefox installed by default. As of bug 7788, Firefox now starts properly in ThinLinc. However, sound doesn't work. After installing the DEB version of Firefox, sound works just fine: https://www.omgubuntu.co.uk/2022/04/how-to-install-firefox-deb-apt-ubuntu-22-04 At the very least, we should update our platform specific note on the topic: https://www.cendio.com/thinlinc/docs/platforms/ubuntu/
https://community.thinlinc.com/t/sound-not-working-under-ubuntu-22-04/529/4
Probably related to bug 2048.