Need basic animation software to make MP4s

After looking at videos online and how most are the same lecture I would give - just on video :dubious:, I’ve decided to supplement my lectures with videos I will make and post online (hence the MP4 requirement). I’m not making the next South Park here, I just need something that can simulate drawing a line, moving numbers/shapes around, crossing out units, etc.

What’s out there that is cheap/free?

There’s a bunch of free ones: List of 2D animation software - Wikipedia