>>26154913First and foremost, welcome! We here at /vt/ hope you have a good time here!
To address your question, a "Deadbeat" refers to a fan of the Vtuber "Calliope Mori" (of Hololive Productions), who is themed after a grim reaper and is known for her rap music, hence "dead" + "beat". It is traditional for Vtubers to have nicknames for their audience that are a pun of some sort based around the Vtuber's concept or name.
Calliope "Calli" Mori and her fanbase are very frequently discussed here on /vt/ (for better and for worse!) so you may come across the term "Deadbeat" quite often! If you'd like, you may also check out her streams and possibly become a "Deadbeat" yourself should her brand of content align with your tastes!
Lastly, and most importantly: don't forget to have fun!
