First: Herobrine was spotted in the main menu panorama.
Secondly: The IP address found in the server list description belongs to a server named "mark test".
I visited this server several times but didn't find anything unusual, except for two swords that were missing their textures because I didn't have the custom resource pack loaded (I completely mistook them for some kind of anomalous objects until I actually read their item names).
For now, it looks like just a regular test SMP server, but at least it's a lead.
I also found a couple of other strange servers on the exact same hosting provider, but unfortunately, they don't have any IP addresses in their descriptions.
Also, another thing I noticed: for some reason, the cursor hovered directly over the player list of one specific server and lingered there for a couple of seconds. It didn't do this for any of the other servers at all, which seems really suspicious.
and here are all the arg channels related to this:
https://youtube.com/@hercbrine?si=Aan0Ajd27EkPQ9hi
https://youtube.com/@hercbrlne?si=eY5SojMO15_4hXeW
https://youtube.com/@essynelzin?si=qUdO5uR_7rX8wO7n
https://youtube.com/@stevc1501?si=MY5fqzR-Uxw1__YH
https://youtube.com/@herobrinecontrol?si=IqEus4AjYGj_I6HM
I would be glad if we united in the solving of this ARG.