Fantastic to hear, #Amethyst is awesome, thanks to the tireless effort of nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z giving us #Android #Nostritches a fully featured #Nostr client.
As mentioned below you have a few options to choose from.
The following note covers the differences between the most common that is worth consideration depending on your motivation for switching.
You also have this article from PrivSecdotdev too:
https://privsec.dev/posts/android/choosing-your-android-based-operating-system/
Beyond that, the same sentiment expressed in the quoted note applies here too, any questions, support etc regards GrapheneOS etc AMA.
Be pleased to work it out with you,
Be well and take care, enjoy your journey.