Sitecake - Drag and drop CMS for HTML websites. It's flat file CMS so it's pretty fast.
Bludit - Bludit is a web application to build your own website or blog in seconds, it's completely free and open source. Markdown support.
ClassicPress - The WordPress fork. No Gutenberg. Great future!
WonderCMS - WonderCMS is the smallest flat file CMS. Completely free, open source, privacy oriented for over 12 years.
Textpattern - Textpattern is an elegant content management system that is free, open source software.
BoidCMS - Flat file CMS for building simple websites and blogs.