An analysis of six popular admin panel gems for use with Ruby on Rails:

• The "original" admin panel -- still widely used for new projects today
• Ruby-centric markup design using Arbre
• Has CSV, XML, and JSON export

https://activeadmin.info/

• Attractive interface using the newest front-end technology
• Paid option adds dashboards / menu editing / inline editing
• Built by Adrian Marin

https://avohq.io/

• Semi-Saas where you keep the database, and the Forest servers only know the tables, columns, and associations. Data is delivered by an agent to the forest servers which render pages.
• Paid option adds visualisation / charting / workflow enhancements
• Lots of traction, having secured significant funding

https://www.forestadmin.com/

• Very lean
• Has GUI Form Builder / CSV export
• Configuration all done in database tables instead of an initializer file
• Paid option available
• Built by Pete Matsyburka

https://www.getmotoradmin.com/ruby-on-rails

• The "original" sexier alternative admin panel
• Has CSV export
• Built by a very dedicated soul -- Mitsuhiro Shibuya

https://github.com/railsadminteam/rails_admin

• Automatically adds routes without having to modify routes.rb
• Offers a Ruby-centric DSL via a well thought out set of helpers
• Pretty lean
• Built by Sam Pohlenz

https://trestle.io/

Also considering adding ThoughtBot's Administrate and Chris Oliver's madmin.

If you get:

The asset "active_admin.css" is not present in the asset pipeline.

then do this:

bin/rails g active_admin:assets

(But it really should already be there.)