The current master has now been released as 5.8.2. There is a fixes-5.8.2 branch for any bug fixes that are needed.
The release notes at https://github.com/polyml/polyml/releases includes a list of the various changes. The major change is the replacement of libffi with the internal FFI compiler. Other changes include the addition of IPv6 structures and PackReal32Big and PackReal32Little structures.
The master branch has been stable for a while so there should not be any big surprises but as ever let me know if there are problems.
David