I tried FFmpeg, but couldn't figure out how to run it. I'm sure that I'm capable of doing so, given enough time to read and comprehend their documentation, but life's way too short, and I have work to do. Plus, I must admit that I've grown weary of techies that stress the technical innards and obscure features of a given system, without ever giving much thought to the end-users, who usually simply want to use the product.
Then I got ShareX, which actually uses FFmpeg under the covers, but that fact's pretty much invisible to me, as an end-user. ShareX has a bunch of extra features that I don't need, but it seems to easily be able to record a browser session to an MP4 with just a few clicks, which is perfect for me.