Flic for pi3..
I am the developer of the Linux SDK so I'll keep a look in this thread at regular intervals.
A quick status update: Since I released the SDK in January I have not had nearly as much time as I expected to work with the SDK. I am thus very grateful that developers continue to report bugs and beta test the library. Instead we have been working with some very exciting improvements of Flic, some of which was released yesterday (The 2.0 release). As soon as this is also completed on Android I'll have more time to work with the SDK. Hopefully the new improvements will also be available on Linux.
Regarding your request: we do indeed aim to make RPi3 the main platform. I recently tested it with the latest release and was able to connect 10 buttons without failure for several days. It's a good idea to try and lower the entry level even more, maybe by providing a installation script for Raspbian.