FWIW, this is listed as deprecated in the Release Notes:

https://developer.apple.com/documentation/macos-release-note... (Search for CoreStorage; their fragment links are hilariously broken)

The premier 3rd Party technical blog Eclectic Light talked about it in June: https://eclecticlight.co/2026/06/17/what-to-do-with-your-enc...

I can't immediately find prior warnings that this was coming.

The following technical note from July 22nd says Encrypted HFS+ Volumes won't be supported in macOS *28*, so this seems a bit early... https://support.apple.com/en-us/125615