From the link in my comment:
Over the course of 2026, we’ll migrate all existing Proton Drive features to the SDK, and build all new features on top of it.
Our priorities are to:
- Complete the SDK rollout across all Proton Drive clients, so the desktop, mobile, and web apps use the same codebase.
- Upgrade Drive’s encryption algorithms to use on‑device hardware acceleration, delivering faster operations while reducing CPU usage.
- Add the still-missing Drive features to the SDK, starting with Photos uploads and downloads, file sharing, devices, and file revisions.
- Gradually move toward a single, well‑documented integration path that third‑party apps can rely on.
- Build a Linux client using the SDK, which speeds up development and keeps it consistent with the other Proton Drive clients.
I guess this only covers Drive and not Mail