I'm so sorry to hear it. I will tell you that I likewise had a lot of final round rejections. The most soul-crushing rejection came after 9 interviews, a 10hr take home, and a 4hr on-site – and through all of it, every decision maker told me they were excited to start me.

Nope, rejection comes 2 weeks after the on-site with no explanations, and they refused to elaborate further.

The sole advice I can give is unfortunately to just keep going. Wish I had more. Best of luck.