[Not Secure] in front of messages

I am on my own paper Aternos server. The following plugins are installed:

AxMinions, CustomOreGen, Essentials, ExecutableItems, LuckPerms, ProtocolLib, QuickShop-Hikari, SCore, Vault, WorldEdit, EconomyShopGUI

Now, my problem: whenever I type anything in chat, it says [Not Secure] in front of my name (only in console). Similiar to a prefix. What is causing this? How can I get rid of it?

On that note, I seem to be unable to properly use LuckPerms. Maybe I'm just too dumb. Nevertheless, I can't seem to make pre-/suffixes work. My guess is that both of these problems are connected with one another.

Please help 😄