If you're interested in game engines using Lua, please also consider Planimeter's Grid Engine (https://www.planimeter.org/grid-sdk/ and https://github.com/Planimeter/grid-sdk) which has been in steady development for about a decade, having even more features than Defold and Solar2D, such as out-of-the-box multiplayer with client-server prediction, Tiled support, configuration bindings, and much more that you'd have to roll yourself in both engines! (and it's MIT licensed to boot.)

No other game engine in Lua is going to provide dedicated server support out of the box besides Grid.

It's all also built on the latest version of LÖVE, which gives you access to all of the software in that ecosystem, too. It's the only full fledged game engine on LÖVE that we know of.

It's less known as we don't do much advertising and have had far fewer contributors, but our focus has been consistent over the years.

Because we have fewer resources, we also work very closely with those using the software if you have any questions.

While a collection of game engines using Lua seem to be tapering off in active development, such as Polycode, Corona, and perhaps now Defold, Planimeter's Grid engine is actively used by the group for game development projects, and will continue to be supported into the future, bringing commercial support in 2021.