First I want to mention I installed Linux Mint 19 on a Mac running Catalina (10.15.5) using Parallels Desktop 15 for Mac Pro Edition and it would not update no matter what we did. Aptitude repositories would not install no matter what. After messing with all the suggestions from multiple forums I gave up and went to reliable Ubuntu (the god father of Linux.. lol). It is always reliable and works no matter if I install it on a laptop, virtual machine or a server. Reason I don't like Ubuntu is the bloatware.. just seems slower than other distro's but when it always works you wonder why you ever tried anything else.
When installing Ubuntu 20.04 on the Mac make sure you configure options and ensure Hypervisor is checked under the CPU section or Ubuntu install will just hang with a spinning Ubuntu circle of death but after you wait for everything to get done, it also fails with a Parallels Tools install because Parallels Desktop 15 for Mac does not support Ubuntu 20 and the newest version of Ubuntu it supports at the time of this article is 19.10 so going to try #3 which is download Ubuntu Desktop 19.10 from the archive and try to install that.
Just as a note, I am seriously considering installing the Arch Linux madjaro which looks totally awesome and I have only read great things about it but to be honest I haven't worked with pac as the software update/installer. I'm familiar with aptitude for Debian systems and yum installer for Redhat systems but pac would be all new to me so let me get Ubuntu working first then play with something new.