At one time there were several Youtube channels that found, cleaned-up, and uploaded public domain training films and other documentary-style educational videos for a grateful audience. wdtvlive42 and Historia-Bel99TV were summarily deleted a couple of years ago. This week the hammer fell on Jeff Quitney who had presented over five thousand films that he had spruced up. Youtube does not seem to have an appeals process. They first demonetized him based on (most likely spurious) copyright claims against music that was part of a few of the soundtracks. Now, his channel has just disappeared. Fortunately he has at least partial backups at Bit.Tube and Vimeo. His goal is to ultimately have everything restored but that will take considerable time. I’ve linked to him many times and have found at least temporary replacements from the Internet Archive as well as from other Youtubers. Still, it is a shame what happened to him.
Periscope Film of Los Angeles still exists, providing watermarked films from their commercial library. Let’s hope they remain and grow.
Addendum 7 April 2019: Looks like he’s making Vimeo his go-to site for old and new videos. Click the image to go to his Vimeo page.