In this release, the assets Administrate requires are now bundled in with the gem itself. You might need to do something to try this release out and we'd like to hear from you about how this goes! Please open an issue if you have any troubles.
We have an open PR to document how to work with custom assets, if that's something you're doing.
The plan is to release a couple of "beta" releases, followed by a release candidate after we've ironed out the migration requirements.