A note on how to run on develop like n00bs like me:
On MacOS, the JUCE libraries are expected to be at ~/JUCE, otherwise you can change them via Projucer > Global Paths
If you originally downloaded JUCE, you’ll have to clone the repo and switch to develop:
git clone https://github.com/juce-framework/JUCE.git
cd JUCE
git checkout develop
Don’t be tricked by the modules saying they are still 5.4.7 in the Projucer — JUCE 6 isn’t out yet 
If you want to confirm you are on develop, you can open up one of the modules and make sure the comment header says 2020 Raw Material (and not 2017 ROLI).
I’m not sure how often people bother building the Projucer, how often, whether they have an alias from Applications to JUCE/extras/Projucer/Builds/MacOSX/build/Debug/ etc…