Audirvana _ on a Rasberrt Pi4 8gig mem possible?

Is it possible to play A+ through a Rasberry Pi 4?

You can use a raspberry pi4 as an upnp device (installing the appropriate sw), Audirvana will discover it and play to it.

On RPi you have other options, like Volumio. Or you can play to it over the network like @stefano_mbp suggested.