If it's not going to be in a kitchen, any sealant will do. The advantage of the butcher block oils such as Waterlox, the stuff IKEA sells, etc. is that you can re-apply it right over the top of the old stuff, after a steel wool rubdown. Pick something that dries fast, which means Waterlox is out. It smells vile, like all tung oil, and takes 24 hours to dry and cure.

Be sure to seal top and bottom (and the ends and sides). Do not listen to the people who say it doesn't matter. I had an IKEA countertop, and I was using the bottom side for stain and finish experiments ... ran into supply problems and stopped the kitchen project.

That countertop warped as soon as the high humidity of our rainy season started. If you put a straightedge across it, there was about an inch deflection between the middle and the edge. Yes, it eventually straightened out, but it's not a good thing.

I think most people, reading your title, would think that your query was going to be about granite sealers. I speculate that is why you got few responses. May want to repost with "wood" in the title.

Rock Hard Table Top Varnish is still about as tough as it gets.