I just “jailbroke” my 6s+ using palera1n on iOS 15.7. You can’t install DiOS from their repo on 15.7 (because it doesn’t support tweaks atm), so you have to install the njb version with TrollStore to install it. Fastmem is still not supported on devices that doesn’t have 4GB ram or more, and JIT can only get activated using non jailbroken methods.