I had heard they had rewritten it in go and got a lot more performant, not sure what else they have done. I don’t care much about the politics as long as it’s still open source (is it?).
That said, I’m a happy nextcloud user and I don’t see a reason to switch (after moving both data and db onto SSDs it’s much faster, so maybe php wasn’t the bottleneck).
While I’m a fan of GrapheneOS, I think it could still be considered “tied to Google” both due to it being based on Android, and also because it only runs on Google Pixel phones. Graphene focuses more on security, then on privacy, but not so much on reducing our dependency on Google’s software and/or hardware.