Hmm, I just installed 0.9.5 from the Kubuntu 16.04 repos (64-bit), and it runs, but when I installed the testplugin 0.1.12 and tried to run it, the error message says "this plugin does not exist" or words to that effect. I blew away the Sigil preferences directory, re-installed the plugin, and got the same result. Even though the plugin was definitely there. Ditto for any of the plugins I regularly use.
However, building 0.9.5 from source worked fine.
Albert