you don't need windows, but that is how I have my install set up, as WINE can be kind of buggy with the program. it doesn't need networking, so no risk of m$ taking info, and SW2024 can run on 8GB and some CPU passthrough.
speaking as someone who's tried just about ever 3dCAD program under the sun, SW is the best on the market for ease of use, documentation, and available plugins.
openSCAD is absolute hell for ease-of-use, onshape sells your data, freecad has the same issues as openscad, and AutoCAD, while good, still is worse than SW due to poorer documentation, and more annoying interface.
of course, there is always the option of doing the drawings by hand on paper, with a ruler, a compass, and a protractor. this may be your best option for sharability, as your local municipality may want to have it for their records as well, assuming that a) they don't already have it, and b) if they do, you were unable to procure the original blueprints.
damn, that thing must be like, a Scottish castle or something LOL.
super cool that you live there!
now I'm confused about onshape though, as anything digital that's "free" has long since enshittefied, and sold you as the product......... could the seriously be one of the last bastions of good free software? it may not be OSS, but if its really that good........ hmmm, food for thought. I'll have to do more research on it.