I assume many people are hard at work to get a free version of something like the xcode build system stood up. It's mostly there already, but I haven't seen anyone put the parts all together in a way you can self-host.
I think iOS hobbyists these days usually use a SASS build system with a free or cheap lower tier.
I think it's perfectly reasonable for Apple to continue prioritizing security and keeping things locked down, but the end user deserves to have a key that can unlock things if they want them unlocked.
It’s an innate limitation, not an arbitrary restriction.
Should Apple really be forced to port their tooling — and the entire, massive software stack it’s based on — to other platforms?
I assume most developers targeting Apple’s platforms don’t kick up a fuss because they’re happy running macOS.
You’re free to produce your own toolchain, developer tools, IDE, etc.
This generally isn’t done because it’s a significant amount of work, and you’ll always be playing catch-up to Apple’s comprehensive integrated development stack.
It’s a large amount of expensive, ongoing work, and leveraging Apple’s native toolchain will invariably provide a better user experience.