A circular saw and a hammer would do it. Just 2 cuts and a thwack per board.
If the cuts are too deep a sawzall and longish blade would work too but take longer.
If I somehow ended up owning this house I’d probably just screw some 1/8” steel straps across the bottoms of the joists and call it a day. The the bottoms of floor joists are in tension anyway.
A circular saw and a hammer would do it. Just 2 cuts and a thwack per board.
If the cuts are too deep a sawzall and longish blade would work too but take longer.
If I somehow ended up owning this house I’d probably just screw some 1/8” steel straps across the bottoms of the joists and call it a day. The the bottoms of floor joists are in tension anyway.