I'm pretty new to editing osm. But maybe tunnel=building_passage could fit as well?
tunnel=building_passage

Ah my bad, I was a bit too generous with the shape there. But the kadaster info isnt completely correct with reality either: there is a little triangle connected to the east of the main house. https://maps.app.goo.gl/faqJs7Wo914a5BUr9

At the same time, maybe my edits at the back of the gardens is wrong as well then. I marked it as where the roofing goes, instead of leaving it open where there is a passage with a door.