Dungeondraft and Wonderdraft, Godot and whatnot. Share tools, mods, assets (mention the license!), etc.
Let’s take advantage of threading: post the tool up top, and any stuff for it goes in a reply. Keeps things tidy. Or creates chaos. One way to find out!
For those into the Rust ecosystem, there’s the Bevy Engine, which is an in-development 3D engine written entirely in Rust