Hello!
My white background has a material with “Depth test” set to false and it’s works, but how to disable depth test for text?
There isn’t an option for that. Potentially you could mess with the internal material use for text to disable depth test but that isn’t recommended.
The recommended approach, and much easier I’d say, is to create a new layer in your project Layers settings, order it to render after your World layer and assign it to your text element (remove the World or any other layer from it).
Also don’t forget to add your new layer to your active camera, so it renders.
This way your text will render after your other world elements render.
Now if you would like it to render on top of everything, and you don’t care about order, then just set it to UI layer. That way it will render last.