NoChatClear is a small client-side Minecraft mod using Fabric. With version 1.20.2 Mojang decided to clear the chat, when the client is entering the configuration-phase. This happens for example when switching to a world with an other datapack, even if it is on the same proxy-server. See this bug, which was closed as "Works As Intended": https://bugs.mojang.com/browse/MC-265250

Usage: Just put in in your mods-folder and it will prevent your chat from being cleared in the configuration-phase.