If I recall correctly, the checkm8 exploit they use is a bootrom exploit, meaning it occurs at a low-enough level exploit that it can only be patched with new hardware. Every iOS version on vulnerable hardware will forever be exploitable.
Hi. Just letting you know, I think this is a shady website. Pangu was a hacking/jailbreaking team, this website has taken that name to lure in people who are looking for a jailbreak tool.
They also have downloads and stuff available but obviously the official sources of such tools should be preferred!
See “iDevice Compatibility” on this page: https://pangu8.com/jailbreak/checkm8/