You can use Copilot Chat* with basically any API provider, and if you switch to the VS Code Insiders build you can configure it to use literally any OpenAI API-compatible endpoint.

Other than that Zed has a similar experience which is pretty decent.

* By which I mean the good one, whatever it's called now - the part of Copilot that used to be a plugin and is now part of VS Code, not the thing that has always been part of VS Code.