If you need install or update your iphone 8 or x you still can use this beta options and download beta firmware that is still signed from iOS15. we don’t know for how long apple will keep this iOS15 firmwares signed. How to use this firmware? just download the ipsw and use put your device in recovery mode using mac or 3utools on windows select the download version and restore.
IOS15 BETAS IPSW STILL SIGNED BY APPLE DOWNGRADE FROM IOS16 TO IOS15
THank Cr. https://www.gsm1x.xyz/