Plenty of great email, contacts and calendar services out there, you just need to pay for them. I went with FastMail and it’s been absolutely painless.
1 can largely be solved with effort (just about) but last I checked Fastmail doesnt use the same vcard formats as Google/Apple and doesnt support custom fields in contacts. That might have changed recently and I'd be very interested to look again if it has.
I even went as far as a fairly engaged back and forth with Fastmail support (reference to which is in my comment history somewhere here) to work out how they could get bi-directional syncing of custom fields to both platforms working. But they had no plans to implement it.
I appreciate mine is perhaps a niche use case but I've got a lot of contacts with multiple addresses and numbers in multiple countries and short of saving maybe 5 or 6 replica contact entries per individual (which is a mess over) the workable solution was to stay within a walled garden.
1. Set up an email client and get into the habit of checking your mail from it instead of the web interface (at least, on your normal devices). 2. Create and start using your new email account, which you can add as a second email address in your client of choice, alongside your gmail. Share the new address with friends and family; people who you want to recieve mail from. 3. Gradually switch over logins and the rare newsletter you care about to the new address.
Eventually, you'll find that you no longer get any mail you care about on gmail. That's when you download an archive (which you think you will look at but actually never will) and delete your account. As a side benefit, you'll likely get to cut down the amount of junk mail you get :)
I've never used Google calendar, but I presume there's a way to export as ical? That should make it easy to migrate to any provider you like.
Fastmail has a decent calendar, but you may prefer to use iCloud or something else for that. Calendar clients on desktops and phones tend to be pretty good at supporting multiple providers so that is a lot easier to migrate.
I trust it because I can get it from 3rd-party repos — Debian, Fedora, F-Droid — and I trust that they wouldn't all allow malicious software that claims all communication is encrypted.
Syncthing's forum uses Discourse. The whole thing just smells of competence.
Of course, it may not suit you.