I don’t trust any e-mail encryption done by the provider (including Protonmail) and there are cryptography nerds who say things like “forget encrypted e-mail, wrong tech, wrong use-case, use something else like Magic Wormhole or Signal” (search for “the PGP problem”, most of the problems have been addressed in at least GnuPG but still, the metadata leakage for example is still an issue).
Unless I really control my end of the channel including choice of encryption software, algorithms, placement and validity of keys, etc. I don’t think it can ever be trustworthy. Protonmail for example even use web crypto which adds another layer of potential insecurity. And that’s just the tech layer, what if my recipient is an idiot and forwards my message unencrypted (because that’s what their e-mail client is gonna allow)?
So I don’t pick my e-mail provider based on how they encrypt, I can use any insecure provider because it’s me and my hardware doing the encryption. If Infomaniak ever goes completely nuts, I can be moved off them in a weekend.
I guess that sidesteps the question but I didn’t follow the controversy back then about Infomaniak because I didn’t care that much, I work with Digitale Gesellschaft and other digital rights organizations to shoot these things down on a political level no matter what a single company thinks. So far DG has been very successful. e.g. they prevented the launch of an electronic ID card that would have been insecure, privacy-invasive and run by private corporations.
Ah, thanks, my contribution is mostly just money/donations and then voting correctly 4 times a year so the government doesn’t get any crazy ideas ;)
I have to say I barely even use encrypted e-mail, when I do it’s just through GnuPG. I’ve used Claws-Mail’s GPG plugin and Thunderbird’s built-in PGP support, works well enough. But I’m not very up to date, maybe you can find better information and nicer tools from e.g. Privacy Guides. They have a section on OpenPGP but it’s dry because this is just a dry topic :(