I may be some time. :-/
I've hosted/supported e-commerce software for more than 15 years but this is the most difficult one to get installed and running. There is no clear installation path/instructions and downright dangerous instructions. Permissions of 777 should NEVER, repeat NEVER be used, for example and is in fact impossible to use where suexec/suphp/PHP-FPM comes in to use.
Using the master.zip directly extracted on the server, installed to web root and with file/directory permissions set correctly to 644/755. Step 4 of installation present a blank (500 error) screen.
On a different server/control panel, I have managed to get something running but the admin is super slow = unusable.
BTW: Thanks for the support, guys.