Trying with 19.10 and so mesa 19.2.8 I’ve noticed a new « bug ».
Launch a web browser on a site with notifications enabled ( firefox & deezer in this case ).
Keep the browser running ( minimized window or other workspace ) now play SuperTuxKart full screen.
Each time a web browser notification pops up, there’s a glitch ( site briefly appears ) and a major slow down in framerate in the game, major enough to interfere in playing.
I did not have that in 18.04. And I don’t have that in 16.04.