How to protect hardwood ply?

I’m making my way through the build of my home office. I’m currently boarding out in hardwood ply. Electrics go in this weekend. We aren’t planning on painting or putting anything on the ply. That’s the finished surface.

I have been advised to apply a coating just for preservation and to stop any fading/yellowing.

I really want to keep the uncoated look. What product should I use and how am I best applying it to avoid darkening or changing the finish?