In consultation with our contractor, we think the fibrous layer under that old linoleum is, in fact, probably asbestos. So we’re going to choose what the previous remodelers of this kitchen chose: encapsulation. We’ll leave it buried under plywood, which is a perfectly legitimate and legal thing to do. We will install oak flooring to match the rest of the first floor, as originally planned, on top of it all. This will leave the finished surface of the new flooring at about the same height as the tile floor we removed.
Another interesting archaeological find this morning: one of the soon-to-be-demolished studs of the closet in the ex-sunroom has part of a mill’s or lumberyard’s stamp on it. I’m pretty sure the rest of this board used to say “<something something> lumber co”.