I wouldn’t self host email. But I would pay for a host and get away from Gmail. Wait until Black Friday and get free/cheap services from a bunch of places. Maybe even proton if you’re okay with them. Also, using your own domain for email is pretty cool (to me).
You’ve got some good suggestions, I think most of the suggestions I can think of. Nextcloud is of course the big one but after using it for quite a while, I think it’s important to break down your needs. If you need file sharing/syncing only, there are better options that are easier and faster. If you only need chat/voice, rocket chat is really lightweight and easy. If you need file sharing, online office suite, chat, etc. Then Nextcloud is the right option. Just keep in mind, even if you think you need some of those things, will anyone but you ever actually use them? No, they won’t, because they don’t appreciate how cool it is to self host and how much effort you put into it.
I don’t know myself, but Graphene OS (on Google Pixel phones) has a pretty impressive sandbox layer for the play store and the apps it installs. It might be worth looking into if you’re not aware of it currently. (But if you’re aware of the Fairphone, I’m guessing you probably know about Graphene).
I will help hand hold anyone who wants to build servers or services (to the best of my ability) to replace Google services with their own.
Someone keeps fixing the CSS color coding of an input field border and someone else keeps copy/pasting the old version when they’re doing basic edits.
“Please enter your password and the name of a random stranger for password authentication.”
Look at all the layoffs they’ve been able to implement with the mere threat that AI has taken their jobs. It’s very profitable, just not in a sustainable way. But sustainability isn’t the goal. Feudal state mindset in the populace is.
You are correct, Graphene only runs on Pixel phones. I know there’s a few open mobile OS options out there but I’ve not spent any time researching them. There is a very good chance if you absolutely need an identification, then you can’t get away from Android. Hopefully someone else sees your comment and has an answer.