The plugin installer will automatically install the Windows 3.01 API so there is no need to install it separately.
It will put the ExtIO dll into a default directory (usually C:\Program Files (x86)\SDRplay) and then you should copy that into your application install directory (e.g. C:\Program Files (x86)\HDSDR)
In order to improve the interoperability between this plugin, SDRuno and dump1090, both of those applications have been updated as well. There have been no other functional changes to those applications.
All of the installers can be found on the downloads page (https://www.sdrplay.com/downloads)
Reason: No reason