Two interviews with two people each.
Talked about technical topics and questions.
The questions generally go into what you have done so far in your career, how you dealt with problems, etc.
Some behavioural questions.
My impression is that they are very tight when it comes to salary (possibly due to their pay transparency policy, so it turns out to be a double edged sword), and I believe that is what stopped me from proceeding.
They really want people who want to work there only because of the appeal of the work, and who are possibly even willing to go down in salary to work there.
I'll leave it up to your as to whether that is a massive red flag or not.