Anything you can play with VLC is able to cast. If you use a client like NewPipe for YouTube, you can set it up to play videos externally with VLC

Privacy was the reason it started, but I was also constantly bothered by the growing annual profits they earned from people basically giving away access to their information and livelihoods for free. I realized how valuable our information is, and the only way to break this deepening centralization and control of it, was to take it all back. Self-hosting and supporting FOSS are my methods to regain control in this war. It has become a sort of holy war for me at this point. Lol