Jailbreaks were quite popular back then and allowed iPhone users to run all sorts of things on their system. The spectrum ranged from minor extensions in the system to the use of apps from other sources.
The Odyssey team has now published the first images of a new jailbreak tool called “Cheyote” via Twitter, which is said to work with iOS 15. The developers announced on Reddit that good progress had been made and that the tool would probably be available in the near future.
Coming soon. pic.twitter.com/CfeyfSiwUN
— Odyssey Team (@OdysseyTeam_) July 17, 2022
However, there is a catch, the whole thing only works with iOS 15.0 to 15.1.1, i.e. with old releases that are no longer signed by Apple and therefore a downgrade is impossible. They are probably also working on support until 15.4.1, but that will probably take a while.