The J801 beta is available for all platforms.
The main reason for the beta is to simplify development of the Qt desktop. This replaces the earlier J7 GTK desktop, which will not be supported in J8. At the same time, the desktop wd interface is updated to match Qt layouts.
For those not making essential use of either J6 wd or J7 GTK, then the new beta will be a straightforward upgrade. In particular, the J engine, J console and JHS are identical in both J7 and J8.