This is the latest unstable release of CircuitPython that will work with the ItsyBitsy NRF52840 Express.
Unstable builds have the latest features but are more likely to have critical bugs.
Every time we commit new code to CircuitPython we automatically build binaries for it. They are stored on Amazon S3 by language (some which may be unreleased.) Try them if you want the absolute latest and are feeling risky.
All previous releases are available on GitHub. They are handy for testing but we recommend the latest stable otherwise.