I’m know you said besides Keychron, but I’d like to validate your statement for you. I have the Keychron K3 Low Profile Wireless with optical Brown, and while it’s been flawless for it’s purpose (goes into the office with me as a mobile keyboard), I bloomin well wish I could get different key caps to mod it.

So you’re right to look elsewhere if you want to build your own rather than just assemble something from stock parts.