Same issue here. I just bought a brand new SM-G955U (AT&T). Steps I've done so far with phone:
1) Turned on phone, signed in with google
2) Signed into Samsung account, setup acct, setup gearS3, samsung pay, then I logged out and signed in as a different samsung user (just to match the google acct).
3) Installed all the Google apps, updated everything, finished hours later.
4) Installed Samsung update, approx 45mb
5) Install Google Launcher from app store. Setup all my shortcuts, font-size, wallpaper...
6) Woke up this morning, opened the app drawer using the Google Launcher, shows no apps, just the words "Search Apps"
7) Switched back to TouchWiz, all is ok, working as normal.
8) uninstalled Google Launcher, reinstalled, still no apps in drawer. Also tried to clear the App-Cache, no go.
9) I tried to install the "Pixel Launcher" from the XDA forums, where it did work fine on my Moto Z Play, still no apps in drawer on my GS8+.
There seems to be some posts on other sites related to the same symptoms, but with older devices from about 2-3 years ago. They point to Knox as the culprit, but no step-by-step instructions on how to permenantly fix the issue.
Anyone? Ideas? Please?!