FOUND! Stop Related YouTube Videos
I found a plugin that will fix another issue I have run into. This problem was caused by YouTube, not the WordPress Editor, aka Gutenberg.
This plugin also will automatically center your YouTube videos, so you won’t have to go to the WordPress Customizer and add the Additional CSS snippet I mentioned in my last post.
This plugin is the YouTube Embed and YouTube Gallery WordPress Plugin. So far it is working well. When you install it, just make sure that you go through the plugin’s Setup Wizard and select the options you need.
Note: The plugin has a premium version, but when I tested it today, I could accomplish what I needed without purchasing the upgrade. Although I am recommending this plugin, I am not receiving any commission for recommending it. All support questions need to be directed to The EmbedPlus Team.