Was it a "plain vanilla" Linux Mint installation from the downloaded .iso?
What did you learn? Did you encounter any issues, bugs, or problems? Were there any special driver requirements? Do you have any recommendations or suggestions for those who will follow in your footsteps? (Like me!)
Added later:
Are all of the ports and interfaces working? I am curious to about Thunderbolt and external display interfaces in particular. I have an underutilized iMac 12,1 (2011, slightly older than yours) and your post got me thinking.