As unfortunate as that is this is not a universal problem, where I live 14/16/18/20 are readily available and competetive in price/TB, and they have been for a few years (at least the 14/16TB ones, not sure about 18/20). One would hope that the roll out of larger capacity drives would also result in more availability in your region - perhaps not of the largest capacity that exists, but at least of a larger capacity than is currently available to you.

XPrivacyLua is no longer maintained YFI. It still seems to work just fine for now, but that probably won’t last. I’ve not found a good replacement for it yet.

I keep my keys on a Yubikey. I’ve not really had a need to use the GPG portion of this on Android, but it works fine on Linux and MacOS.

I used this guide: https://github.com/drduh/YubiKey-Guide