Slime Rancher developers have deliberately chosen not to support the GOG version of their game with respect to free DLCs, unlike Steam and Epic Games Store : r/pcgaming
Slime Rancher is free to claim on the Epic Games Store until March 21 - Neowin
Slime Rancher VR DLC is now out! : r/oculus
Slime Rancher" free on Epic Games store (Mar7-21) : r/freegames
The Cube-News Update: 2/25/19. Featuring news from Halo 4, Firewall… | by Zack Hage | Cube | Medium