O3DE came from Amazon Lumberyard which came from CryEngine, so it's quite possibly one of the better looking open source 3D game engines that you can currently

O3DE came from Amazon Lumberyard which came from CryEngine, so it's quite possibly one of the better looking open source 3D game engines that you can currently get, no strings attached: https://github.com/o3de/o3de https://github.com/o3de/o3de Sadly, you need to put in a lot of work to get good results out of it (neither of its predecessors had a reputation for being easy to work with) and for whatever reason many studios aren't exactly rushing to invest a bunch of time into it (many just go for Unreal Engine 5, or stick with Unity etc., indies often opt for Godot), so you don't get much past simple example projects. Part of this is probably that it never generated a lot of hype or much of a community around it. Godot has a big community around it and is maturing pretty quickly, the early versions were pretty rough when it came to 3D (2.X and 3.X), but it's better now. Not as stable as Unity or Unreal but those have had the advantage of lots of years of work put into them, by more people than Godot has up until now. There's also more niche options like Stride (https://www.stride3d.net/ https://www.stride3d.net/) and Flax (https://flaxengine.com/ https://flaxengine.com/) but they suffer from the same issues as O3DE, even if otherwise are promising.