KiCad is easily one of the best open-source/free electronic design automation suites. Among many other uses, KiCad has been used for System76 in designing their open hardware products . KiCad has been in development going on 30 years now and with KiCad 6.0 is another big milestone.
KiCad 6.0 introduces a new file format, improvements to its user interface, much improved 3D viewer, and much more. This blog post from earlier in the year has a very detailed look (including plenty of screenshots) showcasing all of the changes with KiCad 6.0 compared to version 5 and prior.
The KiCad 6.0 roadmap also has a look at many of the changes to find with this big open-source EDA software update.
KiCad 6.0 has been tagged and currently available in Git form with presumably the formal release announcement out soon on KiCad.org .