Wine - Open Source Software for running Windows applications on other operating systems.
Roll20 - Roll20 is a suite of easy-to-use digital tools that expand pen-and-paper gameplay.
CodeWeavers CrossOver - Don't buy a Windows license, don't reboot and don't use a Virtual Machine. Try a free trial of CrossOver to run your Windows software on Mac, Linux and Chrome OS.
Astral Tabletop - Create, host, and manage your tabletop role-playing games — online or in person
PlayOnLinux - PlayOnLinux will allow you to play your favorite games on Linux easily
D&D Beyond - Official online toolset for Dungeons & Dragons tabletop gaming