Alternatives

Ruby on Rails

See Ruby Toolbox Rails Admin Interfaces.

• RailsAdmin, see this comparison article.
• Thoughtbot's Grayson Wright announcing Administrate, 'a better way'.

OSSERT's project health stats for ActiveAdmin, Administrate, and RailsAdmin

GitTrends stats for ActiveAdmin, Administrate, and RailsAdmin

See also lists on LibHunt Awesome Ruby and Awesome-Ruby.com.

JavaScript

• react-admin (source) 4,900 GitHub stars as of July 2018.
• Motor Admin (source), a no-code (Vue + Rails API) admin panel with forms and reports. Open core with Pro extensions. ~1k GitHub stars end 2021.
• AllcountJS (source) Angular. Unmaintained.
• Rubix Rails 5 API + React.
• Ember CLI Admin for Ember.
• Retool lets you build admin UIs quickly via drag and drop, and connects to databases and APIs. Commercial solution, but also self-hostable.
• KeystoneJS Depends on MongoDB (demo)

Other

• CUBA.platform (source) Java.
• openxava (source) AJAX/Java.
• AdminArchitect, ActiveAdmin for Laravel.
• ExAdmin for Phoenix Elixir, see comparison.
• Forest Admin Hosted solution with no access to the app's data thanks to the open source local plugin.
• QOR for Go.