What is the recommenced iso to use with the PPort

That is not available any more, there is just the Preempt version from Beagle.
Download the stuff from here and install on Linux Mint, should work without to much hassle
www.linuxcnc.org/temp/
Download only linux headers and linux image and Linuxcnc, all 3 only deb packages.
Install by double clicking using gdebi.
Again for older computers, new ones do better with RT-Preempt, some new ones do not do at all !

Yup mine is still there, but might have issues installing it to HDD.
Please do let me know if it works.
I am very sure that as live version it works properly, as i use it quite often.

forum.linuxcnc.org/9-installing-linuxcnc...d-rt?start=10#156413
Id does not have the installer at all, so that must be installed on the live session and then an installation to the HDD attempt.
Most probably it will fail to install properly, that is why i suggested the download and installation of the temp files on a fresh installation of Linux Mint.