How is GrapheneOS / SeedVault looking these days in terms of being able to capture reliable backups and restore them to another device (without using the cloud)?

I gather the introduction of the android:allowBackup="false" manifest flag complicated things somewhat... I thought I read since then that a Device-to-Device (D2D) impersonation mode was implemented, and would love to hear if that helped?

(I posted a couple years ago about this topic, admittedly it was a bit ranty: https://news.ycombinator.com/item?id=37774254)