@jessica@mk.absturztau.be
You connected, but now need to be authenticated with the server. Authentication secures your nick.

Your message after the <JessicaFrem> was successful but not read because of the above. Above your message, you can see a list of other connected users like jroc k4mi israel_b . Above the user list is the channels 'topic' which is subject to change at the moderators whim.

Other channels you can join are Linux, geekhack, llamas, and many others- but I don't recall offhand if any do not require authentication because it's a pretty standard thing for everyone to do. You can set up your client to auto-authenicate on startup.
https://libera.chat/guides/registration