TL;DR: Did phone screen & 2nd round, was convivial and professional throughout. Emailed thanks, a special presentation with thoughts and plans, and asking for an update, and received no response of any kind. Very disappointing, of course, but also disrespectful to my time and effort.
In mid-Dec, 2021, I applied online with custom cover letter and application. Reached out and received a positive, encouraging response within a few days. Reached out again for 3 additional weeks until an interview was scheduled. Understandable due to holidays, but I feel that if I hadn't followed up several times, I wouldn't have gotten a callback.
Phone Screen: Had a convivial, somewhat free-flowing phone screen, learned more about the company than the role. Got some great feedback at the end.
2nd Round: Later that week, had a standard 2nd round chat with someone else, getting lots of details about the role, goals for the department, and asked lots of questions. At the end, this person told me to email them with any questions, and described further steps.
Outreach 1: I emailed a thank you that day with a few questions about startup equity, but didn't get a response.
Outreach 2: Two weeks later I emailed a 10 page deck detailing the principles that would inform my early work in the role, and the concrete steps I would take to implement them. It took 3-4 hours to prepare, used company branding, and was detailed and enthusiastic about the contribution I looked forward to making. I received no acknowledgement of receipt.
Outreach 3: I followed up a week later with a checkin and to see what, if anything, I should prepare for. I received no response.
I put in a significant amount of effort in my application, my preparation for my interviews, and in the presentation I prepared. Even a simple, 'thanks, we've gone a different direction' would be something, To acknowledge this effort seems a small courtesy, and to receive no response at all, after multiple checkins, feels quite bad.