Try the kitchen forum ... and be sure to post a floor plan showing the original spaces and your proposed changes.

So much great advice (and no judgement - thank you!) — I wanted to update, we’ve confirmed it’s only shellac! Thankfully, and we’ll be working on removing as much as possible tomorrow, with heat off and windows open. Pics below, including my husband cleaning his mess lol. Great tips on the floor - you’re points are right on, and given the work the walls will be I’d like an easier alternative for the floors for sure. The left window is actually a door that a previous owner caulked shut, but we’re planning to open and make functional again. Otherwise there isn’t much room for anything, but it would be ideal to move the sink elsewhere to have more wiggle room in the “bathroom”. We did take a quick look today at more narrow utility sink/ vanity combos, and while not perfect should be an improvement. At this point it feels that is still quite far in the future, but hopeful the shellac removal is quicker than I anticipate. Once again THANK YOU, I have been so delighted to find such a knowledgeable (and patient) community!!!

Basement, crawl space, or slab? A toilet takes a much bigger drain than a washing machine. That means adding that 4” pipe all the way to the main drain.

Do NOT put it in the front hall, not only will it squeeze the bottom of the stairs, it will looked tacked on. Or, block the view to your fabulous staircase. Plus, I suspect the water lines are in the back of the house, so it would be expensive. Is the porch enclosed? I can't quite tell from the layout. If so, absolutely steal it from the pantry. Ideally, you'd want the bathroom door facing the porch. But if that is not possible, I would make a tiny butler's pantry area off the kitchen, which you walk thru to get to the bathroom (PD's idea). It would also be easy to vent to the outside, since the bathroom is on an outside wall. And, check the code in your area for bathroom size. In my municipality, a bathroom only has to be 3x5, so you could easily keep 3 feet of floor to ceiling cabinets in the pantry :)