In case it helps anyone, here's a recent blog article written by Daniele Procida (a director of engineering at Canonical, responsible for documentation) that helps explain the motivation for our written interview: https://ubuntu.com/blog/written-interviews - "Not just an annoying list of questions"

Disclaimer: I work for Canonical and help with recruiting.

I'd love it if our hiring process was shorter or tighter, but the written interview part (the part people seem to protest the most) I actually think is helpful. We're a fully remote company, and written communication is very important, so I think it's important that we evaluate how well someone can relate their experience and get technical ideas across. I personally review several written submissions per day, I read them in full, write notes of my thoughts, and evaluate them carefully. So your effort isn't wasted!