Apparently Ventura has created an issue in video playback in the web browser object. YouTube and Vimeo play sound but have no picture. Hovering over the progress bar does display thumbnails of the video at that time point but the screen is blank.
On a site such as CNN, video embedded within their page plays properly.
A form that runs a YouTube video on El Capitan is fine. Same file and form on Ventura is a blank. At the moment I don’t have other systems to check with.
I’ve had another report of that 
And I’ve confirmed that the very same file plays video properly in the Web Browser object on Monterey. So it does appear to be a Ventura issue - and one of the reasons I make myself a sacrificial lamb on the bleeding edge when new operating systems come out.
Your sacrifice does not go unappreciated. I’ll have to update to Ventura shortly to test my current project even though I usually wait longer before going to a major system update. Hope I don’t discover any new anomalies. 