An infinitely wide wing has no wingtips. You suggest it could not
provide lift.

Heck no. It just does so with no *net* downward momentum of air. In
other words, the upward momentum ahead of the wing is equal to the
downward momentum at the rear of the wing.

I've read the "wingtip vortices provide lift" papers,

I'm not proposing that.

the wing causes downwash which provides lift (action-reaction) and
=that= creates vortices.

Infinite wings have no downwash, yet provide lift. By *definition*,
downwash is caused by wingtip vortices.

The higher pressure air underneath the wing has to go somewhere -
around (the wingtip) and up makes sense to me, and that is a vortex.

Except when you don't have wingtips. ;-)