Let me just mention Gopass ( https://gopass.pw ) which is a brilliant terminal-based `pass`-compatible password manager ( https://www.passwordstore.org/ ). Gopass is open-source, free, and based on open standards. Meaning, you can use your keystore practically anywhere. For instance on Android with the Password Store app ( https://play.google.com/store/apps/details?id=dev.msfjarvis.... )
Can I use Yubikeys on iOS and Android? The GPG keys are externally held.
Yes you can. Some YubiKeys support NFC (not sure if that works on iOS though), but also you can use USB-A USB-C converter, USB-A microUSB converter, or just a USB-C or lightning YubiKey, or convert to lightning I guess.