AV1 is crazy-good for encoding screencasts. 1:28 of video, higher-than-HD resolution, less than 2mb. https://bugzilla.mozilla.org/show_bug.cgi?id=1996198#c0
There's not a lot of movement, but many codecs just don't handle that well.
Here are my encoding settings, including skipping repeat frames https://gist.github.com/jakearchibald/39932dee13a10a757b86b853e16ac79f