Htmx does use javascript under the hood, but just makes it so the developer can use html markdown for more a more interactive environment that's driven sever side. So the initial page load should render, but UI elements might not work as intended.
htmx is more a move back to REST as it was originally defined (aka not json backend).
The starting line really puts me off. I don't really care much about the tech content but find their videos entertaining.
I have un-subscribed from all their channels and will see how much this video is addressed in the next WAN before I decide if to continue to watch their content at all going forward.