There's definitely pre-built options out there. On the QMK side you have stuff like the Technik, Keychron, Moonlander, and a lot more. On the ZMK side there's a few options right now but there's some in the pipeline like the new Kinesis 360 "pro" model.

There's also a lot of small companies offering build/modification services if you're not comfortable with a soldering iron but want something more exotic. It's usually not cheap but keyboards are honestly a really expensive hobby.