Debian, like any other legacy distro, mush became declarative, because the '80s model of manual deploy and the absurd pain of D/I and Preseed must end.
In the end, Nix is just a thin veneer on this stuff.
Given how many quick & dirty sed patching or exec commands I've seen in the few nix package/modules I've read, I would not exactly bet my life on it being completely idempotent & reproducible.
it's the best option after IllumOS (OpenSolaris) IPS integrated with ZFS. Far less powerful not imposing zfs (only well supported for root, swap, encryption etc), so not integrated in the package system and bootloader management (BEs, Boot Environments).
It's not reproducible bit by bit, it fetch the current version of anything, but it's still easy to reproduce enough, stable enough and complete enough, while classic distros need a fresh install every major release or facing issues an keeping a system in unknown state for long until it explode.
Proton makes safer, more private (than, say, Gmail) email a possibility for people who don't have much technical knowledge but who know enough to want to keep their emails out of Google's hands.
If you have both the knowledge and time to run a server, by all means, that can make sense (and can be fun!). It's just not as widely applicable.
You send emails to @gmail addresses most of the time, so... How you can avoid giving Alphabet (or some other giant) your messages?
The point of ownership is having your mails in your hand, on your iron, anything who can talk IMAPs or even POP is ok for that. For voice/chat etc Matrix or XMPP might be yours, so nobody could decide to ban you or shut the service down. You still depend on a ISP ok, but much less dependencies anyway. That's the point IMVHO.
While thinking that company X is better in privacy terms than company Y is honestly meaningless, you can trust them or not, you don't know what happen on their servers or someone else ones where they actually live on (like using Amazon o Microsoft cloud as a backend).
Internet is not the web... And we do need to destroy boundaries to break walled gardens not creating new one for the joy of giants who knows their "oligopoly power"...
Radicle is a good answer, coupled with a reborn Usenet, maybe Nostr. We have like never before the ability to communicate and cooperate yet most fails to understand and implement that.
Nearly any of us could run an XMPP/Matrix server and federate with friends or Nostr/{0xchat,whitenoise}, all with audio, video, text, file exchange etc, yet less than 1% do that.
Simply people, techies as well, have forgot the meaning of personal ownership and therefore are owned by someone else.
While I use it in LaTeX I tend to avoid it in non-LaTeX contexts BUT even though it's much used by LLMs having switched to EurKey layout years ago I can type it on my keyboard as well as × and many others, so it's not such a perfect AI indicator.
