Doesn’t this require the person building the code to own a Mac, a potentially expensive computer? Also I recall that years ago there was a $100 fee to register as an iOS developer, though I’ve no idea if that continues to be the case.
Yes, it still costs $100 per year, or else your apps expire after seven days and you can only have three (AltStore hacks notwithstanding—those will get closed soon I’m sure).
There are ways to sign apps without a Mac/xCode, namely Cydia Impactor. But Apple has very purposefully made this impractical for every day use.
If the actual goal is to sideload—which is what was being discussed—you don’t need to compile anything. You’d download a prebuilt but unsigned IPA, and then use Cydia Impactor to sign it with your developer certificate.
If you're ok trusting a third party (such as an alternative app store), they can build it, send you the binary, you sign it (on Windows or Linux), and install it on the phone.
Yes, it does require access to MacOS, and payment to Apple to register as a dev - even aside from having to build apps yourself, this is not a reasonable solution to escaping the walled garden
There is a $99 fee for the Apple Developer Membership. A Mac is only needed to run Xcode, which is Apple's IDE+toolchain for iOS/macOS/etc development. If you want to build from source, you do need a Mac. If you want to install a precompiled app (.ipa file) you can use Windows or Linux.
