Check out Amber, that's the app for handling key security on Android. You save your nsec into Amber, then it will let you sign into other apps and Nostr web apps, keeping your key secure. I also would try Yakihonne, it has great support for long form articles. Voyage is good too, for a lighter text only client, with great discovery features.

https://github.com/greenart7c3/amber

https://github.com/dluvian/voyage

https://play.google.com/store/apps/details?id=com.yakihonne.yakihonne