The "best" self-hosted AI assistant depends on your specific needs, but here are some popular options known for their features and flexibility:

1. **Mycroft**: An open-source voice assistant that can be customized extensively. It is compatible with multiple platforms and has a growing community of developers contributing to its skills and capabilities.

2. **Rasa**: Focused on creating contextual AI assistants. It’s particularly strong for building custom chatbots that require a deep understanding of conversation context. It’s also open-source and allows for extensive customization.

3. **Open Assistant**: Based on the GPT models, this platform allows you to deploy your own instance of a conversational AI. It’s suitable for those who want the capabilities of a GPT-based assistant without relying on external services.

4. **Hugging Face Transformers**: Although not an assistant per se, you can build highly sophisticated AI models for various applications, including assistants. It provides a wide range of pre-trained models and is very developer-friendly.

5. **Snips**: An offline, private-by-design voice assistant platform. While Snips was acquired by Sonos, its technology is still a solid choice for those prioritizing privacy and offline capabilities.

6. **Jarvis**: Inspired by Iron Man’s assistant, Jarvis is a home automation assistant built using Node.js. It’s open-source and designed to integrate with various IoT devices.

When choosing a self-hosted AI assistant, consider factors such as:

- **Ease of setup and use**: How straightforward is the installation process and the learning curve?
- **Customization options**: Can you easily modify and extend the assistant’s capabilities?
- **Community and support**: Is there an active community or support available to help you with issues?
- **Integration**: Does it support integration with the tools and platforms you use?
- **Privacy**: How does it handle your data and ensure privacy?

Evaluating these aspects will help you determine which AI assistant best meets your needs.