My first recommendation for easily accessible soul history are the series of Youtube videos of The Sound Of Motown special from the ITV series Ready, Steady, Go! Shot in 1965.
Hosted by Dusty Springfield it features The Supremes, The Temptations, Smokey Robinson and The Miracles, Martha & The Vandellas and Stevie Wonder.
It’s famous for taking the buoy of The Supremes having a #1 UK hit with “Baby Love” and introducing soul music to an international audience. Notably there isn’t as much an emphasis on The Supremes as would develop shortly (notably due to Dusty Springfield’s literal love for Martha Reeves… and the two other chicks…err Vandellas)
and while we’re on the subject of The Supremes…
…the legendary raised right hand “Stop!” pose was developed for this performance, and became part of pop culture.
Enjoy, while I try to come up with something more substantial to write about.