TL;DR
We had to find a CTF{...} flag in the discord server. I started by looking again at the stickers to see if something is diffrent. Then I thought
about what things could be hidden. First I searched for hidden messages with ``||message||`` but didn't find anything usefull.
I rememberd that I use vencord as daily driver platform for discord and that is has some cool mods. Using some plugin I got the flag-channel and got the flag
CTF{8413595d715a267be0c69074b2123cd8c138efc73712398092dd0026cf874a7a}