AntarcticaI get better than 20fps, more like 50-60 on some tracks on max. (but when I recorded that video just then I was limiting the fps, just in case you were wondering) So that makes me even more doubtful of a bottleneck, considering my computer really isn't that high end. And my graphics card is literally the most low-end part. (EDIT: that probably goes to the ram, but 8GB should be more than enough, and I've never heard of ddr4 being any noticeably better)
I use the amdgpu drivers on Linux. Though the drivers really don't go well with SuperTuxKart, I really see no bottleneck.
Let me tell you level loading times are not improved. The only time improved is actually starting the game, but that doesn't matter in speedrunning. And the cache thing won't either.
As for the map loading times, please don't believe it. I know this sounds bad to say, but they have been saying that every time they change something but there has been no actual improvement for months.
It wouldn't really work because addons are updated all the time.
You can (sometimes) turn off vsync by going into your config file and changing vsync #t to #f, which on Ubuntu is under .supertux2 in your home folder which is also a hidden folder. Although if that doesn't work you can try running vblank_mode=0 supertux2 in terminal. It varies between computers. IMO a better solution REALLY needs finding; faster computers have an unfair advantage anyway sometimes.
On the old Ice in the Hole, after the main secret you could do a jump that takes you above the entire level, making using the secret a lot easier and potentially quicker.
Vertical sync (vsync) basically stops the game running over 60fps or whatever set speed it should go at, which in some cases depends on refresh rate. For some people it is disabled, offering around a 1%-10% speed advantage depending on various factors. This doesn't make a difference to individual levels because it is done by in-game time, but it does affect full game/world speedruns because it is done in real time.
I was talking about Ice in the Hole for the secret, although vsync is for all levels.
It could be that the WR is running without vsync, which speeds things up slightly.
In 0.4.0, there is a different secret involving going above everything pretty much for the whole level.
It should be 08.x and 0.9.x IMO.
In 0.5.1 there is a door. In 0.4.0 there isn't. Not using the door is probably quicker unless you can frame perfectly jump.
You can disable transitions, which save some time. The main level that is different (and far worse in my opinion) is Ice in the Hole, where the secrets are changed significantly. Or it could just be that your computer lags 0.5.1 slightly (it is quite a bit harder to run). Though theoretically 0.5.1 is quicker, generally they are both the same except 0.5.1 is harder for one level.
With big tux it is easy; you get that anyway. I allowed that run as a result. But someone else may disagree...
