> It would be great if we could download the solver manually with a separate command, before running the download command

...Can they not just bundle a solver? For that matter, deno is available as a PyPI package.

> as I'm probably not alone in running yt-dlp in a restricted environment

...An environment that doesn't allow you to install Deno, but does allow you to install yt-dlp?

yt-dlp doesn't need to be installed, you can download the binary from GitHub and run it without installing. You might say that a restricted environment really really should prevent running binaries just downloaded from the Internet, and I agree (malware could do many nasty things to a user's home folder without needing to request admin access), but some people think merely preventing admin access is enough. So for anyone under that kind of restricted computing environment, yt-dlp used to run just fine until Google's changes to Youtube forced them to add a Deno requirement. (Though I haven't yet checked if Deno could also be run without installing.)