Most folks want a clear sealer that has some gloss. I recommend MexSeal (or it may be MexiSeal). It will wear out and scratch off, but that's life.
If you want no change in the surface appearance, I WOULD recommend an invisible and permanent sealer that I sell, but that would be advertising, wouldn't it? :^) So try one of the other sealers and be prepared to reseal often. Porous Plus from Miracle will work for awhile.