I was quite surprised that they introduced a new scheduler and replaced CFS with it in the same step. I would have expected it to become available, then default, then replace CFS. But I guess this should be interpreted as indicating they have tested it extensively already, with very low chance of significant regressions.
Linux kernel 6.6 is available for download right now directly from Linus Torvalds’ Git tree or from the kernel.org website. However, you’ll have to compile it on your GNU/Linux distribution. If that’s not your cup of tea, you’ll have to wait for Linux 6.6 to arrive in your distro’s stable software repositories.