How exactly do you write/test your code on free hardware?

That is bullshit. You always need the hardware, most need a server. There is a difference between programs and applications - ffmpeg for example is not an app, but a program.

Of course you do - but it's not a development cost per platform for any other platform except apple. If you already have a PC (which even for hobbyist devs can be taken for granted), then developing for any additional platform will not incur additional costs - except for apple.

I don't have a PC. I have a mac. If I wanted to do serious game development, I would be forced to buy a PC, if for no other reason than testing.

This is just the cost of development.

You can emulate Windows or Linux on a Mac [1]. You can't emulate MacOS on a PC, because Apple specifically disallows it, as the GP already mentioned.

[1] https://www.macworld.com/article/668848/best-virtual-machine...

Emulation won’t tell me there’s a performance issue on a 3060, or let me modify lighting in realtime in unreal editor. You wanna build seriously for pc, you need a PC.

What's "seriously"? If you just want to get a basic game running on pc, you can easily do so on a vm. Sure, if at some point you need some high-performance benchmarking or specialized tests, you need that hardware. But that's for specific types of games and even then at the end if the dev pipeline.

Whereas, if you target macs or iOS, you can't even start development before you have bought a mac.

Not really on topic but that article from March doesn’t even mention UTM.app? Boo