As noted by others, the recruitment process is long and demanding. As a consequence, there's a chance you'll run out of steam, lose interest or get poached by other companies as weeks and months go by. Unfortunately, this means that Canonical will be missing out on some of the best candidates. Be wary of the written essay, it's marketed as something that all interviewers will read in advance, but in my case no one had read it apart from the CEO. Do consider challenging that part of the process when asked to invest time in it. Aside from clumsy and impersonal HR interactions, the rest of the process was okay. Many of the points highlighted by other candidates are true, though exaggerated probably due to rejection frustration. The big positive is that you'll get to have some interesting conversations with clever folks who are experts in their areas. The interviews are pretty freeform, do some reading in advance and prepare questions on specifics you want to dig into: in my experience, you'll really be able to gear discussions in whatever direction your choose. If you've got a strong technical appetite and are already passionate about some of the areas Canonical focuses on, go through the process with an open mind, Canonical may well be a good fit for you. The company seems to be changing for the better, albeit slowly.

tldr; After hours of interviews and exercises they ghost and give no feedback. I managed to complete Canonical's "early stage" interviews - 4 one hour interviews and 4 exercises (1 written, 2 psychometric, and a coding exercise). Although I had great conversations and loved meeting everyone (best part), Canonical ghosted for 2 weeks despite reaching out to my hiring manager for any updates. When they did respond, it was the most generic email: "We are writing to let you know that we have reviewed your application. We regret to inform you that we shall not be progressing your application further for this particular role". Given the progress through the process I would've expected some correspondence or feedback, but they just send an inpersonal email. If they provided ANY kind of feedback that would definitely get rid of the question marks. Instead, Canonical conveys that they do not care about you or the time you spent in their overly long process, even if you do make it to the further rounds.