Now that building is a marijuana grow house. No idea where used furniture ends up now.
Went in a few times when trying to find something better value-for-money than Ikea for the home office. Their prices were too-good-to-be-true, but not being equipped with a vehicle suitable for bringing home 150kg desks or fully-assembled chairs made impractical.
For operating companies, a lot of old laptops and servers go to e-waste resellers. (It's a mix of waste and sellable equipment.) That often ends up on Ebay.
If you're scrounging for equipment that's a few years old, I've found craigslist to be pretty good if you have the slightest amount of patience, a willingness to toss out an offer, and give off the vibe that you'll make it a smooth sale. (When I sell something on CL, I'm more likely just trying to keep it out of the trash and get it into someone's hands who will use it.)
[1]: https://www.joelonsoftware.com/2003/09/24/bionic-office/
most big cities have a few warehouse-like vendors of used office furniture if you do some searching and visiting locations in person. can usually rule in or out if a place actually has a lot in stock by finding it from google street view and checking the size of the building from aerial view.
I read a lot of books about those times during detentions in the late 90s and early 2000s, and I wasn't there to see it, but the mental image of someone mad they're only going to have a six figure bank or retirement account wheeling a chair with a Xerox on it out the door amuses me, somneone who grew up lower middle class, to this day.
Never any really good deals, just decent deals on mostly lower end hardware.
I know from one case where all the IT equipment was sold to an auction house.