Virtual Tabletops
Many RPG players have migrated over to virtual tabletop (VTT) software during the pandemic. These tools often include multi-person connectivity, drawing features, token movement, and image import. If you want something simple, try out Owlbear Rodeo or Tableplop. If you want 3D, Talespire and Tabletop Simulator are the top two. For the largest feature set for 2D, try FoundryVTT. If you're running official Wizards of the Coast adventure modules, Roll20 and Fantasy Grounds have licenses to sell pre-made content on their platforms, so they'll be ready to go in less time.
Industry giant. It's been around a while, and has lots of supported RPGs.
2D, top down, browser-based. Free, with premium paid features.
Has licensed official WotC adventure modules.
Integrate D&D Beyond with Roll20 and Discord using Beyond20.
"A dream for power users, developers, and hackers" - Cyanomys
2D, top down. $50 for Game Master, who must host the server application. Free for players, who connect via browser.
Highly customizable, thorough feature set.
"For l33t gamers and automation enthusiasts" - Cyanomys
2D, top down, software. Game Master must purchase, then host. Players connect via client for free.
Steep learning curve, but very customizable.
Has licensed official WotC adventure modules.
2D, top down, browser-based, dark mode default. Free.
Smooth, intuitive interface. Get playing in minutes.
Still in development.
[Zip File full of JSON files] 5e SRD Monsters For TablePlop
When you make a new character, click "Import"
3D. Beautiful lighting settings and asset collections.
Primarily a map maker, but other people can connect to play. Supports 3D dice rolling, and chat can be done through Steam overlay.
2D, top-down, browser-based. Free.
Includes a handy campaign journal feature.
Beautiful, snappy, intuitive interface, with pop-out window capability.
3D. VR-compatible. Purchase and run from Steam. $10 on sale, normally $20. All players must purchase.
Import 3D models
Astral Tabletop - NO LONGER IN DEVELOPMENT
2D, top down, browser-based.
Partnered with DriveThruRPG to allow users to import purchased content.
Smooth, intuitive interface. Lots of useful features.
2D, browser-based, mobile-friendly, free!
Privacy and Safety is the default. There are no ads or trackers, and no data mining.
Drag-and-drop interface for lots of functionality.
Honorable Mentions
VTT resources
ArkenForge - Make maps for Virtual Tabletops, or run it on a TV for use as a dynamic grid map with fog of war