My daughters Macmini was struggling with general duties after some OSX upgrades. My daughter couldn’t wait fifteen minutes for the desktop to load so it became a media centre for a spell but it was cactus. So i installed Ubuntu and saved it from becoming a doorstop. It is far better and actually works well. The trick is getting a ubuntu mac iso and just doing a default install which automatically leaves the apple firmware intact on the harddrive. So just pick recommended install options. Initially I thought I had bricked it because it didn’t seem to boot. But the boot process is a little different. Firstly it boots the firmware and makes the mac sound then after a white screen it seems to get going with grub but it isn’t the usual ubuntu looking boot. The happy part is it boots and is usuable again. It is a 2009 Macmini with 2gb of ram so it really struggled before. The other option is not upgrading OSX and I did do that for a while too and it was ok. But eventually you have to.