The FreeRADIUS 3.0 branch was first released in October 2013 and the project has since then actively enouraged migration to 3.0 since a lot of things were refactored and improved after 2.2. However the configuration format was changed (though not so radically) which requires manually migrating existing configurations to this new version branch.
While most Linux and BSDs either provide packages or ports of FreeRADIUS 3 this hasn't happened yet for Debian and its derivatives. Some issues to specific to Debian went undetected due to the lack of feedback by Debian and Ubuntu admins.
Even with some lag, contributors have since then helped improving the situation but if nobody is using and testing it on Debian no bugs will be found there. The snapshot builds are made for this purpose.
Packages for Debian haven't seen the light, that's where the release packages come into play. For Ubuntu another individual has stepped up by offering a PPA with release builds (https://launchpad.net/~freeradius/+archive/ubuntu/stable-3.0)