iOS developer @skadz108 is working on a project called Alpine, which aims to be a CLI & SSH Server tool for iOS without requiring a jailbreak.
Alpine is not a jailbreak or sideloading tool and is intended to run basic command line tools and an SSH server even on the latest iOS devices.
The project is currently a proof-of-concept and unfinished, focusing on providing SSH and Terminal Access, a complete toolkit, and being free and open-source.
The developer is unsure if the project will be fully realized but is exploring the possibility of implementing it for advanced users interested in iPhone and iPad customization.