The default installation of Linux Mint on my iMac went very well right up until the moment it didn’t.
I don’t know the cause, but I did find a few posts online about the problem I had, namely a login loop: whereby the login screen appeared to accept the login details only to show a blank screen momentarily, and then return to the login prompt.
There were comments online proffering a solution in the form of ALT-CTRL-F1 etc. Which is supposed to open a terminal window to allow fixes to be applied. The problem for me was that none of the function keys worked F1, F2 etc.
The big issue for me though was the lack of access via SSH, this isn’t installed by default yet alone enabled. This, to me is a major oversight in the Distro’s design, I am come from a time when Linux was distributed in the mail using Floppy Discs. So GUI interfaces, or X Windows were secondary to the text terminal default, X is, after all, built on top of everything else and is in effect a front end to the real workhorse that is the kernel and associated tools.
In the end I had to reinstall the whole system, which to be fair was no big deal as I am still in the process of playing and setting up, nothing in terms of data was lost or in danger of becoming so.
The take away from my experience was to ensure that the very first thing that got installed on the device was the SSH Server:
sudo apt install openssh-server.
That way should the weird and still not explained login loop reappear I should be able to log in remotely, I hope.