You are best not to put on a sealer on the wood just in case you decide later to cover with a semi-transparent stain as the latter will come off and not blend with the sealer for any length of time.
Thompson's water seal or something similar will help preserve boards and will need to be re applied at least annually.
I am not sure there is a way to do this that will last. I know with raw wood furniture you can condition with tung oil.
Linseed oil. It's thin and easy to smooth on. Just wipe it on with a sponge mop..Beautiful afterwards and it looks like a new stain. It protects it too...I do my beautiful porch floor once a year..