I could say the same about overwhelming number of articles on HN, especially those related to software development, that they are kind of an advertisement. The person also does not seem to be affiliated with CDN provider of his choice [0].
I posted a question [1] to see if there is any interest for octopus deploy alternative (fdeploy.com) but got zero replies. I'm still developing the tool for my personal use though.
Making your decision based on that doesn't make sense, because it doesn't affect FastMail at all. They're not an end-to-end encrypted service. They can already access all of your data without a backdoor (and need to be able to, to provide features like search).
I've been using posteo.de. I haven't heard anything negative about them, they're not terribly expensive, they support IMAP (unlike protonmail), and support is excellent (had issues syncing contacts to a BBOS10 device they solved immediately)