I have solid wood doors stained walnut, which looks dated to me. The trim around windows is white. Can I stain over the doors, say in Ebony, for a more updated look? What color would you paint the trim?
Getting a even color with a stain over a finish is doable but difficult. Fortunately you are choosing a very dark color. Take a look at <a href="https://www.house-painting-info.com/restain-cabinets.html">Restain Cabinets for a New Look</a> for information about the techniques you will need to use. The concepts are the same whether it is a cabinet or a door. If these methods don't work for you then you will need to remove the finish before applying the Ebony stain.
The trim can remain white or an off white color if you like the look. For something different try a light coffee/latte color. It really depends on your wall color and tastes.