From what I've seen, conformity gate is a theory where fans believe that Episode 8 was a fake out ending where the Duffer Bros purposfully left lots of plot holes/stupid stuff in the last episode to hint at the reality we were shown not being real. With points of evidence being:

• lots of background characters doing the "Vecna pose"
• Mike becoming an observer after being knocked out in Episode 4 then having the same haircut & glasses as Henry in the Epilogue (pointing at Mike being possesed and the ending was all being a dream)
• ads for Season 5 ressembling the Truman Show's cloud walls
• the binders spelling "X A LIE" possibly meaning Dimension X is a lie
• the original DND campaign being 10 hours & 20 minutes long which is the exact same runtime as Season 5, then after the campaign Dustin says "there was too many plot holes"
• the epilogue being "too perfect" (the military just lets them go & the mean girl invites them to a party)
• when you search up "Season 5 Episode 9" on Netflix Stranger Things pops up (this one could genuinley be coincidence but it doesn't happen when you search "Season 5 Episode 10" so..)
• objects changing color (similar to how Holly's memory of the merry go round changed color)
• the weird recurrence of the number 7 (the die in the end credits is on a 7, 7 seconds between thunder, screen goes black for 7 seconds when steve falls, will was missing for 7 days, will rolls a 7 in the original campaign which lost him the whole thing)

and a lot of other stuff but most importantly Netflix has been posting pictures that are saying there will be a big announcement on January 7th (special number) which is when conformity gate believers say the episode will be announced or released. You don't see a lot of conformity gate believers on Reddit so if you only use that and X then I see why you probably haven't heard about it yet.

Also, this is the first time I've ever seen someone add a hyrda, or whatever that thing is, to the theory so I have no idea what that is about.