Still mad you're too disorganized to cancel a service before your subscription relapses?
I can think of a few of reasons to dislike Proton, but your reasons are shit.
>No foss clients
The webclient is fully opensource.
>no support for FDroid
Like every email service. K-9 and IMAP.
>no ability to self-host the service.
Why would you want that? If you're selfhosting, there's many other solutions out there. It'd be a waste of their time to develop something already done.
Either way, a third party backend seems to exist
I might be wrong but there are either easy email hosting solutions or complicated and secure ones. There's nothing combined.
I mean there are a lot of easy solutions out there but it's risky even if you have one of these solutions but you're hosting it on a server where somebody else could access it. And even if you're hosting them in your home someone could break in and steal data.
A solution would be to have emails always E2E encrypted. For instance with Pretty Easy privacy (p≡p), since this would also encrypt the subject and a developer even created a script to have incoming emails encrypted automatically.
But this is obviously no ready-to-use solution.
Some folks also started an open source Protonmail backend but this was abandoned at one point.
On the other hand it's always easy to complain but difficult to do something. I mean, we could also try to improve and extend one of the easy solutions in a way that it becomes more secure. But instead we are just here.
I don't understand that this post got 4 downvotes, and I don't agree with this so far.
I'm sorry for you for not being able to backup your data. As /u/ProtonMail said it will require more processing power so this will be expensive, and while I'm sure you don't accuse them of lying to force free users to switch to ProtonMail Plus, the costs will not be at the same scale for a student. As such, you don't want to waste your time with projects from which you won't benefit and I totally respect it.
After your finals are done and as your English is excellent maybe could you involve in ProtonMail's translation efforts, as a sustained effort may lead you to a sustained ProtonMail Plus handle (I hope I won't offend /u/ProtonMail by hoping an answer on this point).
While ProtonMail's server software is closed-source, you may as well register on Lavabit, which is open-source and whose encryption is interoperable, for a 50% cut of 15 to 30$ per year (while they migrate their data), or implement your own Magma server which would fully integrate in the Dark Internet Mail Environment. (I will probably stay on ProtonMail because the UI is great, the roadmap is awesome, and because I want to support their development but that's not the point.)
I don't want to be condescending but I would remind you that ProtonMail doesn't show any ads, has an excellent frontend, a heavy backend development, and that all security features are available to ProtonMail users, such as their hidden service, 2FA, or the hypothetical Yubikey support.
so tl;dr: maybe enroll in ProtonMail's translation effort. I don't think that they keep this feature from free accounts to force their users to pay, so we probably agree about the additional costs (but we'd like to know at which scale).
edit: "ProtonMail is closed-source"→ "ProtonMail's server software is closed-source" (there is still a self-hosted open-source implementation: neutron by emersion, here: https://github.com/emersion/neutron).
These are some valid concerns, but I think it's an exaggeration to call that attack vector en masse "trivial". Mass adoption creates a critical mass. Also, suggesting that everyone go back to gpg is a non-starter. That level of friction for ordinary users has proven to be overwhelming. Anyhow, maybe you should discuss this with /u/protonmail who could respond to this better than I can.
Edit: FYI self-hosting Protonmail is now also a possibility.