It is marked as deprecated in the docs for our recent releases: Errai Reference Guide
Unfortunately I've had issues publishing the docs for our latest release and snapshots. I'm working on a fix and I apologise for the confusion this has caused.
We do not have a specific replacement to recommend. The deprecation of Errai JPA is largely because we don't have the man-power to migrate it to use annotation processors. Using JsInterop with local storage would be my best suggestion.
Max, thank you for the explanation, I just wish I known that a month ago when I used it