Cut the strap shorter.

A Trucker's Hitch may be useful. It's a knot that's used to tighten loads.

An appropriately sized turnbuckle with threaded carabiner on each end(to provide off-axis alignment) could work.

Depending on your strength needs a sinching rope binder, truckers hitch, or power sinch are options.

There always is using an intermediary anchor point to bring the ratchet strap to, forming a V shape between the points.

Possibly some kind of rope knot, clamps, some combination of the two, possibly modifying them somehow, it’s hard to know what to suggest without knowing what exactly you’re trying to ratchet.

Ratchet rope might be what you want.

Big hose clamps?

How tight do you need it? Rope sounds like an ideal solution. Maybe a couple of block and tackle type things.

can't you just pull one of the ends of the ratchet strap all the way down until there's only 8" between them?