If you want something that doesn't require a docker container to run but still supports multiple targets, I'm maintaining a small linux daemon for that: https://github.com/mariusor/mpris-scrobbler

for my use case I think the docker container is better solution. I listen on several different devices so having plexamp send everything to last.fm and use that as the "source of truth" and then the docker container monitors last.fm and resends that info to other targets makes a bit more sense - this way I never have to make sure I have something running on my listening device.