I am using a Pebble Time with the new Pebble Android app on a new Pixel 9a running GrapheneOS and have updated my PT to the latest OS as well, but currently when I go to the Calendar settings to configure it shows zero calendars. I have Proton Calendar installed on my phone and it is syncing, and the Pebble app has the Calendar permission. I tested out installing the Google Calendar app and once I added that, then the calendars I have in that show up, but still not my Pronton Mail calendar. I am not certain if this is an issue in the new app, my running Graphene OS, or perhaps something else?
While I don’t know if / how the Proton calendar can be used with the Pebble Android app, I have a Pixel 9a, too, running GrapheneOS. So I can at least describe what works for me:
I use the Etar calendar app from F-Droid with DAVx⁵ and a self-hosted Nextcloud calendar. This works well with the Pebble, and the calendars show up in the Pebble app settings. Offline calendars with Etar can be used, too.
I think that the issue is from Proton, they are not using Android Calendar local Sync (there is a feature request but no news from it).
The only way I find is to share the Proton Calendar calendar to a calendar app that syncs with the local Android Calendar API, which breaks a little the Proton main goal
I think being able to make the Proton Calendar app the default Android calendar app was something they announced for their 2026 roadmap. Maybe that will solve this?
Sorta. I would never (e.g.) sync it with Google, but a local sync (that doesn’t leave the device) using ICSx5 is just as privacy-preserving (I mean…your calendar items are decrypted on your phone anyway). I just don’t want that getting synced up to another server like Google or Microsoft.
I just set up calendar notifications using ICSx5 and it’s great . I used the share feature in Proton Calendar to get a read-only ICS URL which I imported into that app. Definitely a kludge, but something that’s more than sufficient for me. I have the Proton Calendar app anyway, so I can add an event on there, force-sync in ICSx5 (or just wait for it to auto-sync), and voila it will show up on my Pebble at the right time.
. I used the share feature in Proton Calendar to get a read-only ICS URL which I imported into that app. Definitely a kludge, but something that’s more than sufficient for me. I have the Proton Calendar app anyway, so I can add an event on there, force-sync in ICSx5 (or just wait for it to auto-sync), and voila it will show up on my Pebble at the right time.