Your work is a source of aspiration, so I already thank you for the creation of this project.
I had planned to connect KeePassDX directly to ykDroid but there is a little something that bothers me.
The intent "net.pp3345.ykdroid.intent.action.CHALLENGE_RESPONSE" contains your package name and it would be better to create a more generic intent to harmonize and let the user choose natively if another application is created (and to not replace it if the user does not want to).
I was thinking about "android.yubikey.intent.action.CHALLENGE_RESPONSE", tell me if it's generic enough and if you want to integrate it in ykDroid too.