Hi Moritz,

The release notes for the previous version say "On Mac 10.14 and higher is supported." http://moi3d.com/forum/messages.php?webtag=MOI&msg=11034.1

It looks like 10.14 is probably compatible with your mid 2012 computer https://eshop.macsales.com/guides/Mac_OS_X_Compatibility

- Peer