Everything was fine on 17.04 alpha1, yesterday I installed alpha2 and am having problems with missing window decorations. If I check MATE Tweak>Windows>Window Manager I can see this error message in red: “You are using an unknown and unsupported window manager…”. If I select another one, it fixes th…

I installed Mint MATE and had the same problem, so I have installed Mint Cinnamon and it’s fixed. I conclude the problem lies with MATE configuration.