Hackintosh, aside from the obvious issues with it, is not a way of "building iOS apps on Linux".

No, you can compile directly in Linux. You need to build the tool chain yourself, extract the SDK from official sources, and use third party build tools.

Hackintoshes can no longer publish apps, as XCode checks that your motherboard has a valid Apple ID during the build process.

You can run Hackintosh on KVM just right away, although there are practically no 3D acceleration (unless you opt for PCI passthrough) and the performance is really tearful awful, still, it runs Simulator just fine.

https://github.com/kholia/OSX-KVM

Given that running a Hackintosh often still requires using random unverified kexts from the net, I find it somewhat irresponsible to push applications built on such a system to your customers/users. How can you be certain that none of the kexts is backdoored and the attacker uses this as a vector to add malware to applications?