FOR EDUCATIONAL PURPOSE ONLY, CHANGING IMEI IS ILLEGAL IN MOST COUNTRIES, MAKE SURE YOU CONVINCE YOUR ACTIONS BEFORE DOING THIS.
I DON'T RESPONSIBLE IF YOUR DEVICE IS BROKEN OR THE IMEI IS NOT CHANGED CAUSED BY YOU DIDN'T FOLLOW THE STEPS CAREFULLY OR HAVING A DIFFERENT EFS PARTITION SCHEME.
This guide was tested on Google Pixel 3, different device may also have a different EFS partition scheme, please make sure you adjust it with this guide. Other Google Pixel devices may use this guide without adjusting.
This is a guide on how to activate ur idevice on ios 15 (maybe ios 14 idk) when its futurerestored on 16 sep.
DISCLAIMER: I am very aware people might use this to bypass icloud, but I am NOT encouraging you to bypass icloud.
ALSO: THIS IS RECOMMENDED FOR ADVANCED USERS ONLY, i am not responsable for ur device being broken (tho idk how it becomes broken via this)
also, i've only tested this on macOS, might work on linux tho if u replace darwin with linux and shit.