First of all, I would like to thank you for the hard work you put into the Ubuntu Mate so far. I have returned back to using linux at home just because how convenient and familiar Ubuntu MATE is.
As a LTS user, I have decided to upgrade to 21.04 just because I love the new themes so much.
The only thing that bothers me is, that the yaru theme is icon sizes oveflow the bounds of the window. For example, the cross icon (that closes a window) is not a circle, it is cut at the bottom. I suspect that this issue is linked to the HiDPI (since I use 27'' 4K display).