TL;DR:
Kirby 6.0.0-beta.1 is an early developer preview. We plan for a final release before the end of 2026. Kirby 6 will be a free upgrade for all Kirby 4 & 5 license holders.
Important
Don't use Kirby 6 in production yet
Changelog & Docs
You can find all new features, changes and documentation for Kirby 6 here: http://getkirby.com/releases/6