Izotope RX7 does work somehow (I tried the demo on a crackly low-fi 60's recording, and the results weren't half bad), and then there's the open-source solution
https://github.com/deezer/spleeter (which I haven't tried yet).
Unfortunately I forgot the name of a Reaper scripting project which is intended to do exactly that as well, but it was too nerdy command-line-ish for me, so I never installed it. But maybe you do and let us know how it came out?