I wrote another post about this: Librem 5 apps e.g kik..snapchat..etc
Basically, PureOS will not out of the box support non-free applications.
That being said, Ubuntu Touch supports all of the applications listed either via Anbox or the App Store.
Here are the links to the apps: Whatsapp, Slack, Spotify
More info with Purism and Ubuntu Touch: https://puri.sm/posts/ubports-ubuntu-touch-on-librem5-collaboration/