Minecraft 1.8.x and earlier can't be supported because the resourcepack format is too old. Players using minecraft 1.8.x will never be able to see custom textures, even if the server uses a later minecraft version and ViaVersion/ViaRewind. Support for minecraft 1.9.x to 1.11.x could be added, but it would be a lot of work and these versions are not used often. (And those who do should really consider upgrading their server.) To decrease maintenance time of this plug-in, only the latest patch of each minecraft version is guaranteed to be supported. For instance, minecraft 1.20.6 is supported, but 1.20.4 is not.