PHP Developers & Mods, What's Your Go To Open Source CMS?

I recently build a basic CMS for myself with express/react, it was okay but felt “flimsy” you might say. It seems like all the good CMS options are in PHP, which is fine, I'd like to know what your favorites are and why.

My use case is that I would like to build out an open source CMS with some specific extensions for a niche. I've checked out wordpress (of course) and run through the wordpress track on treehouse. I've also checked out Craft very briefly, I liked it but wasn't too impressed with their price point or examples of work done on Craft. Still on my list are Bolt, Drupal and TYPO3.

Feeling some PHP fatigue so any pointers would be useful.

edit: I will need a database, so flat file is not a great option.