Kagi has their own AI assistant that let's you choose any model from the major, and some not so major, providers. You can even hop between them I the same chat. It is also able to search for results using Kagi. This includes any lenses you could configure.

It's worked extremely well for me. Their higher subscription was less than ChatGPT + Kagi. I haven't used Gemini on its own interface yet to compare, though.