SDK / Is there any API to "copy to clipboard" ?

A plugin can run a utility program to copy text to the Mac or Windows clipboard:

https://community.adobe.com/t5/lightroom-classic-discussions/copy-to-clipboard/m-p/8859782

To allow the user to copy displayed text, a couple of my plugins use edit_fields() (which do allow copying). To make them read-only so the user won't accidentally change the displayed text, I use LrView.bind() and a transform function that discards the user's input. 

Here's a function that makes a scrollable-text control using that approach:

local function scrolledText (args)
     return f:scrolled_view {width = args.width, height = args.height, 
        horizontal_scroller = false, 
        f:edit_field {immediate = true, 
            height_in_lines = args.height_in_lines, 
            width = args.width - 12, 
            value = not args.readOnly and bind (args.key) or  
                LrView.bind {key = args.key, bind_to_object = prop,
                    transform = function (value, fromTable)
                        if fromTable then return value end
                        local orig = prop [args.key]
                        prop [args.key] = ""
                        prop [args.key] = orig
                        return orig end}}}

The magic is in the transform() function at the end. 

And he's an example of invoking it:

scrolledText {key = "result", readOnly = true, width = 450, height = 100, 
    height_in_lines = 80}