My question for that is how to figure out what the workplace looks like before you interview.

Ask the recruiter. This is a common question. I've had them blow it off as dress nice but I usually ask them to tell me what the hiring manager is wearing (recruiting often dresses nicer)

If its a software company then I'd guess the default is T-shirt and jeans. If its doing software or tech inside a larger business organization then it may be business casual (khakis, collared shirt). You may be able to check the companies website or social media accounts to find pictures of the workplace.

If all else fails or you still aren't sure just ask the recruiter.

See if they have any team photos on their About page or elsewhere.

In the case of tech, generally you can just dress how you normally dress. Or watch Silicon Valley if you're unsure.

You should have a backchannel before you’re even in the system.

In that case you've already got a leg up and a faux pas or two will probably be forgiven.

this is why we have a diversity problem in tech, because we only hire people we know who came from our exact background.