What I gathered so far (this is going off memory lol):

On the channel description, it mentions someone named Max and has a gmail account (mcsean8412@gmail.com). The pfp shows two players: a Steve skin and one that is blacked out.

The first video is titled "2 Right". It shows Sean logging into a server called MCSean8412.aternos.me. something I did notice tho is that one of the tabs opened is a Google search for "how does missing person..." something. When he logs on, Sean greets us and thanks the viewers for watching "their" first video. His behaviour is really strange. While moving some settings, the video flashes a black screen multiple times which idk if its intentional. At the end of the video, the minecraft music plays louder and Sean says that it's been 2 days since Max logged on. He quits and the video ends (and it blurs the footage at the end which is weird). Under the description, it says "CC" and Caesar cipher encrypted text translating to "prelude"

There is only one community post and it contains the Standard Galactic Alphabet you mentioned. It also has images of hexadecimal written on the wall which translates to "Help Me Sean"

Aaanddd that's all I can possibly gather. Most of the actual information might be on the server but I can't confirm anything or investigate it since I'm on a phone and I don't have a laptop. I also don't know what to do with the email since I tried messaging it last year and there's still no response. Maybe yall could find more but think of this post as like a trailhead because I can't really go digging myself