SMTube 18.11.0 should land in the main repo soon. This fixes still more Youtube playback issues, as well as add a rather weird reverse player option to play the video using a web browser. The reason given for this was that you can then use browser extensions to download the video, though the tried and true method of downloading by using uGet as the player in SMTube still works fine.
MX had been using SMTube 18.9.0 from the antiX stretch repo, but this upgrades over that.
MX 17 Repository: The SMTube Thread
Re: MX 17 Repository: The SMTube Thread
We now have SMTube 19.6.0 in our main repo, which fixes the latest monkey wrench that Youtube has thown into the playback gears.