I have an interesting work around for that in my sidechat tool (https://github.com/day50-dev/sidechat/blob/main/sidechat/sid...)

It's an inversion. Instead of the user selecting and then having to figure things out, they declare an "intention to paste" and then do the selection.

In practical terms, they invoke the "use clipboard" feature then the code probes all the clipboards (tmux/primary/emacs/nvim/clipboard/secondary) and the user selects their text. One (or more) changes. That's the clipboard it's going to use.