There‘s UTM SE on the App Store, which might be ok to use for very minimal distros (no JIT): https://apps.apple.com/at/app/utm-se-retro-pc-emulator/id156...

If you had a second spare iPhone, you could run it semi tethered with JIT and just any ARM/x86 OS: https://docs.getutm.app/installation/ios/

Though a JB would be more convenient. And things start to get interesting with M1 and its virtualization support.