* Gemini for iOS (https://github.com/pitr/gemini-ios)
* Rocketeer (https://lists.orbitalfox.eu/archives/gemini/2020/002812.html)
For Android, Ariane is available on the Play Store and for direct download:
* Ariane (https://oppenlab.net/pr/ariane/)
I had a brief look at the iOS ones but haven't checked how well they do in the protocol test suite: gemini://gemini.conman.org/test/torture/