I'm pleased to report that I have successfully converted my 2015 iMac 27" that Apple has called obsolete a while ago into a walloping #Linux powerhouse running #Ubuntu. The process was much simpler and the result much more impressive than expected. That an obsolete Mac can be turned into such a cutting-edge Linux platform says a lot. Pending issues: no sound (except via BlueTooth) and keyboard annoyances (which were solved by bringing in a wired PC keyboard). My computer is born again!