I think its technically experiemntal, but ive been using this since day one with no issue

Openwebui is compatible with the firefox sidebar.

So grab ollama and your prefered model.

Install openwebui.

Connect openwebui to ollama

Then in firwdox open about:config

And set browser.ml.chat.provider to your local openwebui instance

Google suggests the you might also need to set browser.ml.chat.hideLocalhost to false. But i dont remember having to do that