House Of Leaves was published in 2000 and Backrooms originates (as far as I can tell) from like 2011? Not that it's impossible that the ideas developed independently, but given how big a cult hit House of Leaves was I'd be very surprised if there wasn't some direct lineage. Not trying to gatekeep, it's just that the Backroom trailer was giving me _really distinct_ HoL vibes. I wonder if that's just the film mixing in ideas that weren't necessarily present in the original copypasta.

edit: Another thing I will say is that I've noticed both HoL and Backrooms seem to act like a kind of shibboleth for a particular demographic (not even really the same demographic) and you often see this in how people write/talk about both. I think it maybe stems from how dense/unapproachable the two works are, how innocuous they seem on the surface such that you really have to sink some effort to get at them.

I said to a few friends that the recent trailer felt like it could be for a House of Leaves movie. Different overall setting, but the "found footage" aspects, and the narrative over it, felt like they could be right out of the Navidson Record.

I don't have any real proof for this, but it feels like House of Leaves inspired a lot of the people making "found footage" and "creepypasta" stuff one the internet in the 2000s and early 2010s (SCP, Marble Hornets, Slender Man), and then that stuff came together to inspire the Backrooms.