Another extension that's similar to the deprecated OpenWith is External Application Button: https://github.com/andy-portmen/external-application-button
Maybe it's helpful to also look at this extension, though it's a lot more complex than OpenWith. Just sending selected text or URLs as is to local scripts (or applications like IINA, VLC etc.) or downloaders like yt-dlp, in a direct and simple manner, should imho be the first step, if this is to be implemented in Orion in some form. If needed, additional settings and tweaks could be added later. (In my view, any complexity & parsing etc. should primarily be added by the user in the local script anyway, not within Orion.)