Repost of isaiah's release on Discord:
After a few public releases last week, this build focuses on squashing a handful of small bugs—and a few big ones.
All new add-on installer,
Multithreaded updater,
Mini web server with PHP extras,
More Info Here: https://yourhead.com/appcast/beta/Stacks/devlog_6.0.0_beta_48_6277.html
It should download via the auto-updater soon. Or download it directly here: Stacks v6.0.0 Beta