WordPress, Jekyll, Publii, Bludit, Drupal, Directus, Gatsby, Joomla, DEV Community, ProcessWire, MODX, WonderCMS, HTMLy, Flextype, Nibbleblog, Zimplit CMS, PhileCMS, Sphido, ClassicPress, Section CMS, LotusCMS, razorCMS, Leeflets, feindura, Zotonic, BaferCMS are some alternatives to Flatpress.