I probably wouldn't use one. Unless the ridge is big enough to trip over.

THis is just a summer cottage, no insulation, heat, etc. it was built by a farmer for my parents 50 + years ago. The pine floors aren’t even tongue & groove, just very irregular boards, and I have no interest whatsoever in the time or expense of refinishing them. The vinyl plank is purchased; my only question is about the type of thrasition to orde.

To my eye two different wood floors as shown above always looks like an addition or an afterthought. "the problem is that the wood in the house has been there for 10+ years and is very sun faded" This isn't a problem! This is a great opportunity to redo your floors, since that will need to happen soon anyway. :-) Lay new flooring in the living room (of the same species as the rest of the house) and stain it whatever colour you want. Either refinish the rest of the house at the same time, or if your budget doesn't allow for that plan to do it in a couple of years. It will still be possible to match the new living room floor at that point. Alternatively you could endure the carpet until you can afford to do the whole house. You might have to live with a mismatch for a while, but in my opinion that is better than planning for a mismatch! Especially considering your floor is nearly ready to be redone.

Where was the leak (what was its origin)? What other issues/requirements do you have for a kitchen floor? The overwhelming majority here will tell you to go with wood flooring. But if that isn't something you want, then a tile could be a good choice and you will have loads of options in porcelain or even slate/stone. But really, what matters to you is what matters the most. I wanted cork in my remodel (love the look and feel of it) but couldn't find a pattern that worked with my space and I'm pretty sure my dogs would have destroyed it in a short time.