[MrLeap]

There are tons of answers to this! I'm going to say that in projects I've worked on, LODs have been hand made about 60% of the time.

There are tools for creating automatic LODs that come with their own pro's and con's. A bad LOD chain can express itself as really obvious pop-in while you're playing the game. There's also these things called imposters that are basically flipbook images of an object from multiple angles that can be used in place of the true 3d geometry at a distance. Those are created automatically. They tend to be like 4 triangles but can eat more vram because of the flipbook sizes.

Unreal engine has nanite, which is a really fancy way to side step needing LOD chains with something akin to tessellation, as I understand it. Tech like that is likely the future, but it is not accurate to describe it as the "way most games are made today"