Two-part auto clear coat should be about the best you can do.
About eight years ago, when I made the dashboard on my MG out of tiger maple and African mahogany, I researched coatings. Found a couple places that were testing them over many seasons—one in S. Florida for use on salt water boats and the other in like Idaho or Salt Lake City, making pickup truck bed slats. Each guy was using an array of different products, coating both pine and hardwood test boards left out in the weather for three or four years.
The best setup then was Minwax spar urethane as an initial coat for UV protection, followed by several coats of Pelucid. So that's what I used, brushed and then ragged on with thinner over several days, and it's held up beautifully.