Blockstream Senior Software Engineer interview questions

Recruiter screen who could not tell me what compensation would have been, except "a lot". First round screen was with a product manager from Europe, though I am based in the US. Not sure why they didn't do it with a real hiring manager. My expertise is in scalable systems but they asked me a lot of UI/UX, security, dev ops questions. They wanted someone with all of those skillsets -- I have never seen anyone with that in my entire career. Definitely thought this was a waste time, would not recommend most people to interview. Also they could only accommodate 1-7am roughly my time for interviews.

4 steps which took a little bit more than a week , than two weeks waiting time the for the "offer". First step was a standard HR screen , chat about the company overall and my skills. Second step was an interview with the Engineering Manager about the actual project and my motivations (felt more like a personal fit interview). Then a homework project which fit the company's profile. Last interview was with the current Tech lead about the homework and some general questions about architecture and the used technologies. Then within a few hours the HR person called back to get my details. Everyone was super friendly and effective to get the most out of the interviews. Then the waiting begun, with the last HR call getting my details was to "prepare an offer" waited a week and pinged them that I haven't received anything. After a couple of days HR get back to me to inform about that they are waiting for some higher level approvals etc.. Than another week after that got a cold email "Thank for your interest..." Since everyone was friendly and told me to ask questions after the interviews if i have anything i did that and asked about the decision to provide some proper feedback beside the template response , and haven't heard back since. I don't mind the rejection, but I mind the non-transparent communication and really hard to improve without a feedback (especially if all the interviews were positive)