For rts games, i recommend the spring-engine. Its kind of date visually, but the core multiplayer tech is rock solid.

There is a fresh fork developed by the team behind https://www.beyondallreason.info/ and they are working on performance improvements. In addition, you get the whole infrastructure developed by that team for free (Server tech, matchmaking, map editors etc.)

Its hyper specialized on RTS though. Dont try to make a jump and run with it. Although they tried: https://www.youtube.com/watch?v=a1D295mRqdE https://www.youtube.com/watch?v=kNGe4KTdVN4 https://www.youtube.com/watch?v=-FnmQUgR5RQ

Ludum Dares are pretty hard core engine tests, as in can you iterrate, pivot and check wether its fun quickly. Unwieldy beasts do not survive that.

Unity and Godot are the most popular choices, based on my time spent hanging out with other indie developers. If your game is a 2D RPG, RPG Maker is also a great way to get started. You can also use GameMaker if Unity and Godot seem intimidating.

Hard to say without knowing what kind of game you want to make. I would say look to the games you play that inspire you and to which you aspire to make, then look up what engine they use. For instance, I really like Nuclear Throne and might some day try to make something similar. If I did I would use GameMaker since that's what they used and thus it can probably let you do a lot of what I liked about that game with ease, such as the ultra-juicy hit feedback.

If on the other hand you like Slime Rancher, well it uses Unity and probably that would be a better choice than GameMaker for that kind of game.

I also second Godot though, which is not widely used by many projects but seems awesome to me and totally capable of moving a 2d game out the door quickly.

If your priority is shipping it, and it's multiplayer, then Unity 100%. I don't actually really like Unity, but it's definitely battle tested enough to ensure that you can do everything you need with it. GameMaker is a reasonable choice as well, I just wouldn't be as confident with their networking stuff. Would recommend against Godot. In my experience you end up spending more time fighting the engine than developing your game.

Just my personal thoughts though, others will have had different experiences.

If you're looking for something where you don't need to worry about licensing fees and is good for 2D, checkout Godot. The language used is also very close to python syntax which is nice

Let's set up some expectations first.

Games almost never "get out of the door quickly", with very few exceptions.

That goes multiple for multiplayer games.

What you might be able to produce quickly is prototypes. "A moving rectangle which shoots circles" - kind of thing. That is a super power, don't underestimate it.

LÖVE is a nice game engine, I used it a lot in the past, mostly for personal stuff. And released some open source libraries in the process.

Maybe consider https://github.com/Planimeter/game-engine-2d? We have multiplayer with client-side prediction out of the box. Example code is included to demonstrate the ease of networking entity fields, and there is an included payload abstraction for creating networked events.

You can set the tick rate for your game based on your needs as well. And prediction is robust, supporting exceptional packet loss and smoothing over latency concerns for player movement.

Even Godot doesn't support multiplayer networking out of the box: you have to write it yourself.

I'm using love2d, which is good if you want to see only code, no graphical interface.

If you're interested in using web technologies for your game, you may find the framework I've been working on to be interesting: https://docs.hathora.dev/#/

I've had success using it as the backend+networking stack in conjunction with game UI tools like Phaser and Pixi.js.

ebitengine is "a dead simple 2D game library for Go". I like it.

Godot, Defold, GameMaker.

Check out what people are using for Ludum Dare compo.