There is talk of getting anbox support, though I don’t think it will be available at launch.
This would allow running Android apps from PureOS.
I have no idea whether LineageOS will work initially, but it should be possible for the Lineage community to make it work, since the info about the Librem 5 should be very open. It would just be a matter of getting the development support they need, unless there’s something I’m overlooking.