Thanks for all the hard work going into the server update Spec! Here's the error code I get when trying to log in, if it helps.
Internal Exemption: io.netty.handler.codec.EncoderException: java.lang.Null PointerException: Cannot invoke "com.github.retrooper.packetevents.protocol.item.enchantment.type.EnchantingType.getId(com.github.retrooper.packetevents.protocol.[;ayer.ClientVersion) because "enchantment" is null.