My late 2012 MacMini i7 is running Yosemite 10.10.5. I have some apps that need at least 10.11, but I've read reviews saying upgrading to High Sierra, the newly released OS, is not recommended.
Is there a way I can install a newer version until such time as the newest one has been out a while?
[EDIT]
Unfortunately I have not previously downloaded any macOS installers for El Capitan or Sierra.
Best Answer
Since you've clarified that you've never downloaded an installer for a later version of macOS, then you've only got three options:
There may be other workarounds open to you. For example, if you have access to another Mac (yours or a friend's) that is not capable of running macOS High Sierra, but is capable of running El Capitan or Sierra, then you could start your Mac mini in Target Disk Mode and set it as the default startup disk for the other Mac. Then you could use the optioncommandR startup keyboard combination to upgrade to the latest macOS that is compatible with that Mac. You'd have to make sure you select the Mac mini's hard drive as the install location.
Of course, I can't stress enough how important it is you have a backup regime in place, be it via Time Machine or some other solution.