You have to start with freshly sanded floors. All of the old dirt and finish must be removed first, before you can apply any protective finish. Those are nearing the end of their life, and need professional refinishing. DIY with a sand through the tongue will cause them to need to be replaced.

‘Poly is out of the question’ why? What is your end goal? Tons of different floor finishes available, but most do start with a freshly sanded smooth floor. You want it exactly like it is but shinier? Like it is but waterproof? I suppose you could do a wax or tung oil over what you have but it wouldn’t be considered finished by a future purchaser (which is fine)

You have 200 year old white oak floors to work with. The flooring looks to have plenty of life left since it has been covered with carpet. No signs of cracks along the groove side. Start by sanding as suggested.

Have a pro come in and look. Will you be using rugs over it?

Check what kind of finish is left on it now. If denatured alcohol takes it off, it's probably shellac. I've temporarily rescued a floor like that by using a large orbital pad sander I rented and then putting a coat of shellac over it. It rejuvenates but doesn't give a professionally sanded finish. Does your floor have beveled edges? You'll have to scrape them out by hand.

I guess we are just looking to protect them from weather etc going forward. This is an old cottage at a lake. Think weekend getaway or summer house. Only used a few months out of the year. I took poly out of the equation due to it not lasting on the floors of my current home.

Poly is one of the most durable of protective finishes. If it has not lasted at your home, then something was wrong with that application. You should easily be able to get 10 years out of it before a screen and recoat.

I use Orange Glo on my old schoolhouse wood floors, sprayed directly on the floor (small areas at a time) and then gone over with a Swiffer cloth. Or you can spray it on the Swiffer cloth first. I do it once or twice a month. That is if you want to leave the floor as is, i.e. not sanding and using poly. My floors have the old patina that I love, so I've never had them finished. Depends upon what look you want.

Orange Glo is one of the worst possible contaminants to floors or furniture. There will be zero guarantees that they can be refinished after the contamination that stuff causes. Orange oil is actually used as a furniture stripper, because it dissolves finishes. And it will do that from the inside out, when it cannot be removed from the floors. It ruins them completely. They cannot be refinished without it all peeling off like a bad sunburn.

The oak floors from the 50's, all under carpet since mid -60's did not have any finish at my mom's house. The original finish was a wax, put on with a buffer by the builder. My mom happened to stop by when he was putting on wax. My mom would have to put on wax twice per year to keep finish. If you don't want to do poly and only use home rarely maybe a wax could work. You can still buy small, vacuum cleaner sized buffers.

" I use Orange Glo on my old schoolhouse wood floors "

Do not use that witches brew, you will never be able to refinish the floors, aside from using nothing but Orange Glow repeatedly, they will be trashed once the finish needs to be redone.

So do you actually live with old wood floors or do re-finishing of old wood floors? How did you repair the floors when you came across those that had Orange Glo, etc. used on them?

When I tore up the carpet and old linoleum in my house 44yrs. ago and exposed the original schoolhouse floor, I used Murphy's Oil Soap for awhile. But it seemed to dry the wood out. So I started to basically use nothing but a damp mop occasionally. Like I said, I prefer the old patina that has a bit of a shine and didn't want to or never will "strip and finish" them. Whatever the old timers used on these schoolhouse floors has lasted over a hundred years. Plus they were covered with carpet and linoleum from 1939 - 1978.