I grew up with some of the original bands here (Love, The Foundations--Ozzy is just a bit after my time; that Charles Bradley version is so authentic that it sounds like an original). Your overview is very illuminating.

Here's a cover from the classic period that I didn't know was a cover and then found that the cover far outshone the original.

Folk duo Ian and Sylvia had a minor hit with their wistful, bittersweet (more sweet than bitter) ode to missed opportunity, "The French Girl." https://youtu.be/XmSkGJn6ptM

Former Byrd Gene Clark transformed the song into a haunting exploration of miscommunication and alienation: https://youtu.be/Az-QceoF3JI

Bob Dylan also covers the song, but his version (in my view) is relatively negligible.