Broken rendering of glxgears on S/390 architecture (64bit, BigEndian)
Unfortunately rendering of glxgears on S/390 architecture (64bit, BigEndian) is broken on Mesa 19.3.3 here. It should look like this instead. I bisected the issue and the git commit id d17ff2f7, which came in between 19.2 and 19.3, caused the issue. After reverting this commit, glxgears rendering is working again.