How do I import (Snaps HD) Assets into 2019 without overwriting project or upgrading to HDRP?

Question says it all. I have a 2019 project, not HDRP, and I don't want it to be (I'm still not there yet), and I want to import assets from the Snaps HD asset package (or any package, this applies to them all). But of course when I try to import it warns me of overwriting my project.

I've used these Snaps assets in 2017 and 2018 packages, so I know they can work without being HDRP, but I don't know how.