Criteria like “founded in the last Y years”, “has fewer than N employees”, “has market cap under $X”, “is in a fresh/hot industry” alone or in combination end up including dramatically different sets of companies.
You can be a 0-day 1-person company but if you have a business model and an operating structure, you're not a startup. Most companies are started on a specific business idea and planned to run for long term on that idea. Those are not startups.
Since I have other issues also with not having Nvidia GPU, I can't wait to dump this hardware.