i play on version 1.20.4 and just added this mod to my modpack via curseforge. i checked twice if its the newest verion and it is

i cant upgrade the backback in the smithing table. i can put the backpack in there and put the iron upgrade next to it but nothing happens. i tried it with different backpacks and in creative mode, but it doesnt work.

You can check recipes on wiki, leather is necessary in template slot

OMG that actually worked 😲 It wasnt like that before in another modpack, so i didnt think of that, thank you 😊