What is good Linux software for voice assistance?
There are different dimensions to this question. In terms of assistance, there is speech enabled accessibility software for disabled people. In terms of assistants, there are bundled AI systems for desktop users.
Generally, speech technology consists of output in the form of Speech synthesis (text-to-speech), and input in the form of Speech recognition(speech-to-text). Bundled AI systems are a complex melange of speech technology, lipsynced avatar animation, and artificial intelligence in the form of natural language processing.
I would say the Festival Speech Synthesis System is by far the most popular speech synthesis application for Linux. And, CMU Sphinx seems to be the most popular speech recognition system for Linux. Most modernbundled AI systems for desktop users are built for the Windows platform.