Browser extensions like Copy as Markdown can alleviate conversion needs on desktop, but not as much on mobile.
Adding auto conversion to core, like how pasting works on Github, would expedite pasting URLs into the Markdown editor. Mobile would benefit more with its limited plugin capabilities. Do any mobile Markdown editors have this feature?
I'd like to see feedback on adding this feature to core from those preferring bare links or only using Rich Text. How discoverable and usable would they (and other affected groups) find the Paste as plain text keyboard shortcut or menu item?
This similar feature request is also worth accounting for: Create link with text when pasting a link while text is highlighted