I remember watching these cartoons by Max Fleischer as a little kid on some tape. Also watching them on Toonami after a movie was over and they still had some time left over. They even used the sound byte “We won’t be intimidated by criminal threats.” for some of their ad’s on Cartoon Network. Some of this I think is also used some of the ideas in these cartoons for the DC comics like in 52.
You can also look them up anywhere since they’re public domain too. Also I found this one site where the person stitched the cartoons together as one big movie. You can also burn it to a DVD-R as a Windows Media file as well. These cartoon were very imaginative and aged well into period pieces so give them a watch when you can, you’ll be glad you did. Also here’s the link for the Superman 1940’s movie cartoons so you can download it and burn it to disc. https://archive.org/details/TheAdventuresOfSuperman