Wagtail Alternatives

CppCMS is a free and open-source, high performance web development framework. CppCMS is not a content management system but rather a C++ web framework that has been designed for rapid web application development.  Applications built with CppCMS are capable high loads with high request throughput.

Tina is an open-source site editing toolkit and headless CMS for React-based sites like Gatsby & Next.js

Squidex is 100% open source headless CMS, built by passionated developers. With Squidex both individuals and organizations can handle content for the new web with ease. Squidex modular platform allows users to create content APIs that can be consumed by any frontend framework or technology in a matter of minutes. The framework itself can also be extended and tweaked to suite individual use-cases. Squidex is provided as a fully open source software released and free of charge, for the self-hosted community edition. For organizations that want to get up and running fast, commercially hosted solutions are provided.

Anchor is a super-simple, lightweight blog system written in PHP. Compressed, Anchor CMS weighs in at just under 250kb making it an extremely light weight content management system. With Anchor CMS, you can manage content in HTML or Markdown, depending on which you prefer. The content management is fully free and open-source and released under the GPL-3.0 License.

Joomla is a free and open-source content management system written in PHP. The CMS is built entirely by volunteers from all over the world and has a strong community that provide educational resources, and extensions. 

Nucleus CMS is a PHP-based content management system for the small websites and blogs.

A static site generator with a great back-office for users.

Tiki Wiki CMS Groupware is a free and open-source content management system and Wiki software. Tiki has been downloaded over a million times by businesses, governments, non-profits and individuals worldwide to take advantage of its flexibility and customizability to deliver a broad range of web applications and wikis.

MODX is a free, open source content management system and digital experience platform. The CMS gives you full control over your creative, editorial vision and the experience you deliver. MODX is written in the programming language PHP and supports both MySQL and Microsoft SQL Server databases. The CMS is openly developed and released under the GPL license, and allows contribution.

Backdrop is a full-featured content management system written in PHP. The Backdrop CMS allows non-technical users to manage a wide variety of content. It can be used to create all kinds of websites including blogs, image galleries, social networks, intranets, and more.

Grav is a modern free and open source flat-file content management system. With Grav, you can publish content and build sites in a fast, flexible and simple manner with the file-based web platform. Grav requires zero installation and is just an zip archive that can be extracted to start using the CMS. Grave also comes with a powerful package management system that allow you to extend the feature set of Grav CMS. With the package management system you can install and upgrade themes and plugins written specifically for Grav. The software is written in PHP and released fully free and open-source under the MIT License.