I don’t know, Blender has definitely become slower in many areas, but an UNDO of 30 seconds?
I have a 8 year old pc with a graphics card that can’t even be used to render anymore and one undo step with 2 million verts takes between two and three seconds (still slow, but I rarely use undo anyway..).
What you describe makes Blender almost unusable! This is not my experience…
Viewport splitting still works, on any of the 4 (rounded) corners even.
