You can now test version 6 of KDEs Plasma Desktop by using the unstable edition of KDE Neon. Not all distributions offer an easy way of installing Plasma 6, for now (for good reasons, too).

I only know of one other distribution, that offers an easy way of testing a Plasma 6 version: KaOS: https://kaosx.us/news/2023/kaos04/ (Feel free to add comments to other distributions or e.g. wiki pages with easy installation instructions).

Be aware that in any of the above versions, there will very likely be lots of (smaller and bigger) bugs, as this isn’t even considered an Alpha-Release, yet, and still heavily in development.