If playing a survival map without cheats enabled, even the basic commands in chat will not work. These might include /tell or /help.

Steps To Reproduce:

• Create a new survival world with cheats disabled
• Type </tell test> in chat
• See error message "Cheats aren't enabled in this level"

The following commands are available to all players in the Java edition, without cheats:

• /?
• /help
• /me
• /msg
• /seed
• /tell
• /trigger
• /w