Help with 1.21

Hello si i will be hosting a new Minecraft Server with my friends which we do every year and yea we wanted to use the Stellarity LITE End Datapack the problem it doesnt work in 1.21 i already did some stuff like removing all the s from Function, advancement and the 3rd one i forgot what it was but doenst matter like i said i dont really know what is going on and why it doesnt work i already asked in the official discod server from the pack but nobody could help me