I then edited the wp-config.php file to turn on debugging and then attempted the same thing again.
The error comes back as:
Fatal error: Call to member function wp_rewrite_rules() on null in /var/www/html/wp-includes/rewrite.php on line 150
I tried to find it in the php file, but I got lost in the logic.
This exact same error occurs every time I would try to click "customize" on any theme in the default configuration or any theme I try to add.
Has anyone else encountered this? (and more importantly, were you able to get past it?)
Thanks to everyone that pauses to think on this for me and the rest of the community. I would think that someone has WordPress working properly by now.