Not ideal. We absolutely need to stop discussing if something is “private”. It matters in what way something is private, and by what means. It’s irresponsible to issue blanket statements such as “Signal does not provide privacy.”
Signal provides content-privacy by design: post-quantum end-to-end encryption, on native clients with MITM protection.
Signal provides metadata-privacy by policy: it can collect metadata if it wants, but it has a policy to not do that, and court documents to prove it doesn’t collect it. You need metadata-privacy by design? You’ll want something that’s P2P over Tor, like Cwtch.
I’ve written about this in The collective misunderstanding of Privacy vs Security vs Anonymity
In other regards the article was a positive surprise, no shilling of Proton’s products, well written and balanced. The only issue (in addition to the “not private“ claim) I saw was lack of notion that all software that has ever been written, has bugs, and it’s enough the vendor responds rapidly to reports. If that’s the case and the product isn’t constantly full of holes, it’s the best you can expect, and Signal definitely ticks both boxes.