Sorry for necro, but this is one of the first search results for this issue. Possible cause is Forge checking for zlib (the expected hash) and not accepting zlib-ng (the actual hash): https://github.com/PrismLauncher/ForgeWrapper/issues/3 One possible workaround (aside from swapping zlib-ng for zlib which might cause other problems on your system) would be to use the prism flatpak.