Grumman-581 writes:

I would think that welding a 2" receiver hitch receptacle to the
bottom of the angle bracket would give you more flexibility.

Agreed. I may modify it later like you say, but for now I just wanted the
minimum cost and effort to tow a small boat, improvising a step bumper like
on a pickup truck.

Bumper-mounting a 2-inch receiver strikes me as an awkward combination,
like hanging an oxen yoke on a pony.