I was showing some students the wonderful AsciiVideo example that comes with the Processing IDE and it didn’t work on Linux.
I remember having this problem a few years ago and reading about a GStreamer 1.0 so I found this: https://github.com/processing/processing-video/pull/84
Downloading the zip file, from the pull request above, video capture came back to life again, hurray! 
Now, what can we do so the the library people download from the IDE works on Linux again? 
@villares, the GLVideo library has been superseded by the latest beta version of the processing video library. But that was released almost year a go and there seems to be little progress on that front since. Note that you may need to adjust the sketches to work with the beta version of video library. But now it seems there may be issues with Mojave MacOS with this version. It seems to me that linux has never been a priority with the processing foundation, and progress on the video library is non existent.
Thank you so much, @monkstone, for your reply and additional information! I really think I should be doing more ‘outreach’ work to attract skillful Linux people to the community.
Now that you mention MacOS I have a few students on MacOS Catalina who can’t even run Processing Python mode, it is a sad state. I feel bad I don’t have the time & skills to contribute with these issues.