This seems to be an issue with whatever plugin you’re using for Youtube. Please try installing https://wordpress.org/plugins/enable-jquery-migrate-helper/ to see if that fixes the issue.
For more information on what this is all about, see https://wptavern.com/major-jquery-changes-on-the-way-for-wordpress-5-5-and-beyond
If the plugin helps, please contact the developers of the plugins or themes noted in its admin messages.
thanks steve, that’s got it.