Having not done this yet, but in the contacts app (preferences) you can define/configure āonline contactsā.
In the dropdown list there is an option with name āImap and SMTPā.
Maybe this route can help you achieving your goal.
Also, when you have Evolution installed, you can export the addressbook into a vcf file.
Perhaps you can import that file into Posteo.
EDIT
I just checked: Posteo offers vcf import (see screenshot).
In Gnome 46 it is supported when I tried it sortof worked with Mobian. For L5 byzantium and even crimson based on the supported Gnome version in bookworm I donāt think CarDAV plugins in the online accounts will be available.
My guess is the only way to support it and which has worked for me is using Evolution server plugin. You can install it from the software store, setup using evolution app, then it will sync with your Gnome Calendar, Contacts just fine.
I am hosting nextcloud, and have addded the nextcloud account to PureOS. Calendar, contacts and storage works. I believe nextcloud uses caldav at least
I was able to remove the debian pkg for gnome-contacts (v42) and install v46 via flatpak using the flathub repository.
Gnome menu => About Contacts shows v46.0 installed. Iām still unable to create contact groups or use shift-click to select multiple entries for bulk deletion however.
Group contacts:
Long-press a contact, active the Ctrl key on the keyboard, select other contact(s), then press Link. (Iāve only tested this just now, so I donāt know if itās easy to useā¦ or to ungroup after the āundoā button disappears.)
Delete multiple contacts:
Long-press a contact, activate the Ctrl key on the keyboard, select other contact(s), then press Remove.
EDIT: Actually, you donāt even need the Ctrl key. Long-press one, then long-press the rest.
EDIT2: The Link button may only be for consolidating numbers to one card, not for messaging them all. Disregard
Iām on the desktop.Is CTRL key the equivalent of a long press?
EDIT: Nevermind, looks like long click on the desktop works the same. Once I enter the contact selection mode with the check circles on the right, I am able to use Shift-Click to select multiple items.