Smarthistory is an excellent free resource which I have used extensively. Created by art history lecturers Dr Beth Harris and Dr Steven Zucker, it is the official partner for art history to Khan Academy, an on-line American non-profit educational organization founded by Salman Khan in 2008.
I first used these short videos when taking The Arts Society course In the Footsteps of Gombrich which ran in Truro a few years ago. More recently, I have looked at them closely before going on art orientated holidays in Italy. Last September in Venice, my geek of a husband used a Khan Academy video in conjunction with headphones to play the video on his phone as he stood in front of a piece of art in a church or museum. Of course, if you are interested in coming on our visit to Vienna in May 2021 (http://theartssocietyfalmouth.org/downloads/2019-2020/VIENNAKLIMTTASFALMOUTH.pdf) you will find information to whet your appetite from Smarthistory by searching for ‘Smarthistory Gustav Klimt’ and ‘Smarthistory Vienna Seccession’.