I am still trying to install Ubuntu 20.04 on my late-2011 17" macbook pro. I need to install Ubuntu alongside my macOS High Sierra install that currently is the only other (meaningful) occupant of the 2TB SSD.
The issue (for me) is that the Ubuntu 20.04 installer incorrectly concludes:
This computer currently has no detected operating systems.
I currently have rEFInd installed on this machine - which I did in anticipation of the Ubuntu install.
Why does the Ubuntu 20.04 installer fail to recognize the huge 750GB APFS partition as an installed OS? Is there anything I can reasonably do to "help" the installer see this, and install Ubuntu in the proper location?