Here it's how the resourcePacks list looked in 1.20:

resourcePacks:["vanilla","mod_resources",...,"hordes-config",...]

Here it's how it looks on 1.21:

resourcePacks:["vanilla","mod_resources",...,"E:\\Modrinth\\profiles\\Test 3\\config\\hordes",...]

Due to this path to the config pack, I can't ensure the correct resource pack loading order in the modpack, which has the Default Dark Mode pack, that provides optional dark GUI textures. It must me optional so the players can turn it off, so I can't just put dark texture in Hordes config.