You seem to have enough room to fit in an 80m dipole, so you could go with that & feed it with an open wire feeder from an ATU.
Alternately, you could use a trapped dipole, or a fan dipole.
For a vertical, you could put a trapped vertical on your roof & have some elevated radials, or mount it on a shortish mast on the ground, again with elevated radials.
Even a ground level one with radials lying on the surface should work.
My suggestion is, for a first pass, slap up a dipole.
When I finally got around to HF, the first thing I stuck up was a 20m dipole--- not very high, maybe 20ft above the ground---I called it my "glorified clothesline"!
I had a lot of contacts with it, though!