That's an interesting dilemma when you bring up Android. I have always considered android device as a hardware compromised device and that it shouldn't be used for highly confidential data to an extent that you might be using PGP/GPG for.
But you could have all of your PGP/GPG centrally managed on a Linux system with android device having it's own unique keypair that is signed by your root PGP/GPG keypair on your Linux system. As for software for managing GPG/PGP on Linux system, I just simply use KGPG which does the job plenty well. If you have to use PGP/GPG on Android Phone, then I recommend sticking with f-droid repository for PGP/GPG key management app, not Google Play Store.
Few use-cases for GPG/PGP on android is encrypting email or chat, but application integration is limited to select few software like K-9 Mail or Conversations.
--Edited to add--
Why the heck did server spam duplicates of my comments? :(
keep them in my NC and just import them to thunderbird
Sounds like a good idea, and was considering it. But curious if there is other or better ways.
If they don't need to be accessed often you could also put them in an encrypted folder or file using veracrypt
OpenKeychain is great for keys on Android. It's FOSS and available on FDroid. +1 for using a self hosted Nextcloud instance to keep things in sync.
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
That's an interesting dilemma when you bring up Android. I have always considered android device as a hardware compromised device and that it shouldn't be used for highly confidential data to an extent that you might be using PGP/GPG for.
But you could have all of your PGP/GPG centrally managed on a Linux system with android device having it's own unique keypair that is signed by your root PGP/GPG keypair on your Linux system. As for software for managing GPG/PGP on Linux system, I just simply use KGPG which does the job plenty well. If you have to use PGP/GPG on Android Phone, then I recommend sticking with f-droid repository for PGP/GPG key management app, not Google Play Store.
OpenKeychain Source Code
OpenKeychain Package on F-droid
Few use-cases for GPG/PGP on android is encrypting email or chat, but application integration is limited to select few software like K-9 Mail or Conversations.
--Edited to add--
Why the heck did server spam duplicates of my comments? :(
keep them in my NC and just import them to thunderbird
Sounds like a good idea, and was considering it. But curious if there is other or better ways.
If they don't need to be accessed often you could also put them in an encrypted folder or file using veracrypt