If you're using one of these computers with OS X Mavericks or later, you can install macOS Catalina. Your Mac also needs at least 4GB of memory and 12.5GB of available storage space, or up to 18.5GB of storage space when upgrading from OS X Yosemite or earlier. Learn how to upgrade to macOS Catalina.
And since mid Feb 2016 I own a Mac Mini mid 2007 (macmini2,1). A second hand one. While working with Lion, I discovered it's not supported any more and looking for a way to get it running on a newer version of OS X, I stumbled upon SFOTT.
IMac (Mid 2007-2020) MacBook (Late 2008 Aluminum, or Early 2009 or newer) MacBook Pro (Mid/Late 2007 or newer) MacBook Air (Late 2008 or newer) Mac mini (Early 2009 or newer) Mac Pro (Early 2008 or newer) Xserve (Early 2009) Any Mac that shipped with Mac OS X Mavericks or later will not be compatible with this installer. While searching for a compatible graphics card, I found that I could install Mojave on my MacBook Pro Mid 2010 model by using a software known as macOS Mojave Patcher Tool. Kudos to DosDude1 who developed tested, and released it as a free app. By using this software, we could install the latest macOS version on early 2008 Macs. 2) Follow the instructions to create a USB drive with the patched macOS installer on it. 3) Turn off the machine. 4) Plug in the USB drive and turn on the computer to do a cold boot of the Mac, while holding down the OPTION key. 5) If the USB drive can cold boot, you should see an orange external drive listed.