This is my first time modding anything, so maybe just skill issue.

I'm using Forge 54.0.12 and Temurin 21.0.5+11-LTS

I wanted to create a custom keybind and to check whether it works I'd like to send a chat message. I tried using

Minecraft.getInstance().player.sendSystemMessage(Component.literal("test"));

but IntelliJ couldnt resolve sendSystemMessage(...).

Since I saw people using it in earlier versions, I tried the same thing with 1.20.6(- 50.1.0), where it works fine, now I can't figure out if this is intentional and whether there are other options for sending chat messages.
On that note, is there more documentation than https://docs.minecraftforge.net/en/1.21.x/? It seems very incomplete compared to something like the Oracle Java docs

I figured it out, you just use

Minecraft.getInstance().player.displayClientMessage(Component.literal("Message"),false);

or how sendSystemMessage() does it in 1.20.6 with

Minecraft.getInstance().gui.getChat().addMessage(Component.literal("Message"));

Suddenly clicked that I can look into classes to see how they work