Applied by email, heard back after few weeks, had an text chat interview in a private Slack channel, got an exercise, had a couple of more chats about my exercise. Got a rejection email with good feedback.
The whole process maybe took a month.
Good things:
I liked being interviewd in chat, I'm more comfortable typing than speacking face to face.
I learned how WordPress plugin development works.
I got reminded about commitment and attention to details.
What could be better?
I think they were expecting too much from me. I'm a developer with a full time job, and fixing all the issues in a broken WordPress plugin during my free time wasn't easy. If I were a plugin developer or were I even applying for that role, it would be fine but for someone without that experience it's a lot to expect.
I envy those who can pass that test, but for the rest of us it's easier to just skip Automattic.
As others mentioned, it's a long process. Some days or weeks passed between the time I sent my assignment and the interviewer came back to me. I get it, they are busy like any other company, but it takes too much stress for applicants to wait for such a long time.
My advice is get hands on experience on WordPress and its plugin development before applying.