I know you said not continuity, but that’s literally what you’re describing. I highlight text on one device, copy, and can paste it on the other device.
Not clunky. Just works.
Otherwise, I guess you could just save a txt file on a network share, access it through the Files app, and use that as your “Universal Clipboard”.
Whoops, perhaps I need to learn a bit more about this Continuity thing. I just perceived it as something where it would constantly be talking between my phone and Mac without any input from me and create a security issue. I absolutely think of iMessage that way and that belief has largely been vindicated but maybe the Continuity is a little more secure and less full of security holes...