That’s what I do at the moment with my Nextcloud and there are plenty of services which offer this. But I would like to switch as much as possible over to end-to-end encrypted services.
if you want to self host
@forwardemail apparently has caldav too.
https://forwardemail.net/en/faq#do-you-support-calendars-caldav
But I doubt it is end-to-end encrypted. And also I’m not sure it is has a web interface (including tasks).
I have prolonged my Etesync subscription. After a quick reply that payment was received and a question about my data that I answered a day later, I’m already waiting 8 days since I replied to their question. Several emails later my subscription is still not activated but my money is gone.
Is there anyone else havign trouble with their service?
Is there any other product offering encrypted contacts sync besides Etesync and Tuta?
I guess ProtonMail can also do contact syncing and I assume it is E2EE.
Sorry I mean syncing to the device-wide contact list on Android for example. Not just contained to its own app. On desktop it might be less relevant, but I think the Protonmail Bridge also doesn’t sync contacts to Thunderbird.
The problem with self hosting radicale or nextcloud is that it’s not e2ee, so if someone gets access to your server while it’s running or just powered off, you’re cooked.
I’ve been thinking about hosting the radicale instance directly on my phone (GrapheneOS) since at least I have it always with me, it’s more secure than a server, and it reboots every now and then. From what I searched it seems feasible, I will give updates on the set up later.
Not sure how expensive (as in battery) it is to have a running Docker instance on a mobile device 24/7. 
What’s the issue with self-hosting?
Do you have intruders at your place? You can always secure your rack into an isolated room if it’s a concern. 
If you’re really concerned, don’t store the contacts on any digital device. Or maybe keep them into a password manager!
Seizure by law enforcement. It happened to me arbitrarily in the past (completely at random, I’m not an activist nor criminal) and yet they snooped in all my data.
I do self host, but I prefer self hosting e2ee apps (ente, rclone crypt, cryptpad …)
On my mobile phone I have the self erasing password, which I would give law enforcement, plus the hundreds of mitigations that just don’t exist in a linux homelab.
Of course I could keep it in Proton, but I’d lose many nice features from the integration with contacts and calendars on device, like birthdays, sync with other apps such as WhatsApp (with storage scopes), etc.
What bothers you in that situation?
Loosing the data itself (and need to rebuild it) or them having access to it?
I never checked on Linux, but there might be a way to have a kill-switch. But again, destruction of (potential) evidence? Not sure about the law on that regard.
Definitely software solutions existing. But…with enough money and time you can probably still get inside of a well encrypted digital device.
What bothers me is law enforcement or anyone having access to it. I could just do backups for data loss.
On Linux it’s very easy - once they get access to the server - to take the encryption keys on the RAM. Even if the machine was turned off they can still retrieve it for hours. I explored the possibilities of hardening but it’s not there yet.
On the GrapheneOS phone it’s a bit more expensive to get access (they would need 0 day exploits or very destructive methods), and I’m pretty sure the password to erase everything would be effective (they would probably try the password I give without thinking about data erasure). It also goes to BFU with auto reboot, which would be very cumbersome for a linux homelab but fine for a phone that stays with me all the time.
I just noticed that TrueNAS Scale now has a community docker image of Radicale. I am setting this up now.
I had troubles with the sync and they didn’t reply to my e-mails. It’s clearly abandonware.
Since Etesync has become abandonware with next to no code maintenance and communication having become an afterthought I wanted to move away from Etesync in a way that minimizes risks on data leakage and maintain my privacy in other aspects as well.
As there is pretty much no other application that hosts both a calendar and address book client side encrypted, choosing any online service runs the risk of being read by third parties. Also, in terms of security I think the biggest big tech companies would be safest but they also invade your privacy the most, by far. And any company hosting stuff for many clients is an interesting target for hackers. Then there is the option to rent a NextCloud instance or so. But that still has many of the above risks. Privacy concerns mainly concern three risks:
- Data leakage/hackers
- Privacy invasion
- Authorities using either illegal or legal power
I decided the latter was a lesser risk (for now) than the other 3, seeing that I live in West Europe. So I decided to self host. First I thought about Radicale but there seems to be a reasonable amount of users experiencing problems. In the end I decided on Davis, a SabreDav fork with a really nice UI and decent feature set. So this is how I did it:
- Tried to install myself but I didn’t get it to work. I’m no Docker expert. I installed Yunohost and installed Davis as a Yunohost app. Installation works nicely, but it needed one modification for my dav clients to be able to connect. Can be found in the issues for the specific Yunohost app repo on github.
- I had 5 agenda’s to migrate. I exported every calendar seperately in an .ics file. I then disabled the Etesync app.
- I then created the agenda’s in the Davis user account. If you need to share agenda’s between accounts then that’s no problem BUT first fully create the agenda’s before you share! Any changes in display name, color etc AFTER you shared are not automatically available for the account you shared with. I needed to navigate to the user account I shared a few agenda’s with → agenda’s → open agenda shared with account → manually add the edits. A small point of improvement for Davis.
- Installed KashCal for caldav sync and import of the exported agenda’s. Connect your account. The dav endpoint is
<davis local domain>/dav/. Then in the settings choose import appointments. You can choose the file to import, then the new agenda in Davis to import it to. This way you can restore all your agenda’s. - I use a different calendar app (fossify) because it has a widget feature I really like. After the steps in KashCal you can install Davx5 for sync . Then the agenda’s could also be found in the Fossify agenda.
- On my partners phone I also did these things. That was a new phone with GOS and no contacts yet. I exported all contacts on the old phone to a vcf file (warning: Google Dialer supposedly uses a very old format that is not compatible with new apps). It can then be imported with the GOS contacts app or any other supporting this. Be sure though to choose the carddav enabled account and not local phone storage.
You have now succesfully migrated away from Etesync or any other service you want to get rid off 
It takes some time but it’s very doable in an afternoon or shorter.