I received an email from a "senior recruiter" inviting me to an initial interview. I was asked to fill out a (not-insignificant in length) "Tech DNA" thing and respond with my availability. I did so within maybe half an hour of receiving the email? Never heard another word from anyone at Upstart.

This recruiter never responded to schedule. I waited a few days and emailed to prompt them, no response. I started emailing daily wondering what happened, no response. I eventually emailed their HR department directly to see if maybe my recruiter got hit by a bus or was fired or something. I've had that happen before, one time a recruiter literally had a heart attack and I got lost in the shuffle, and one time a recruiter accidentally deleted my resume and no one noticed. No response. Clearly they have no interest in actually interviewing me, or treating candidates with anything resembling basic respect or courtesy.

What is your availability for an interview? This was the only question I was asked.