I tried the new version of STeem with some demos and games. I discovered something real good. I have always used the "Auto framskip" mode in both STeem and Hatari. I tried to use the "Draw every frame" mode instead.
Much better, much of the tearing disappeared and it's just a little left, so little that it's actually bearable to run Atari ST again. On slower scroll speeds you don't noticed any tearing at all.
Now to the odd part, in Hatari i see no difference at all when using the "draw every frame" mode instead of using auto skip.
How come it works that well in STeem but not in Hatari?
I'll better add, i use the auto frame skip mode in most emulators and that's why i didn't thought of to try this earlier.