I haven’t been manually installing localhost WordPress Multisite installations for a few years, so I was quite excited to see what had changed. So after acquiring MAMP Pro, I installed a single site WordPress and thought to convert it to Multisite in a second.
But after a minute those sweet memories were back: the infinite WordPress Login Loop.
So glad I remembered a certain post from Tom McFarlin about this issue and after a single copy/paste, we are back on track.
So thank you very much, @tommcfarlin.