Adding your Nextcloud calendar and contacts on your Mac
The Calendar and Contacts apps on your Mac work directly with your WebOké Nextcloud, because Apple supports CalDAV (for calendars) and CardDAV (for contacts). You add one account in each app, and after that everything syncs automatically.
Step 1: create an app password
Your regular password won't work here: your Nextcloud asks for an extra code when you log in, and the calendar or contacts app can't enter it. So create an app password instead. You can read how in Creating an app password (needed to connect with apps and devices). Then keep your username and the app password at hand.
Step 2: add your calendar
Open the Calendar app on your Mac and click Calendar in the menu bar at the top left. Then click Add Account...

Choose Other CalDAV Account... and click Continue.

Under Account Type, choose Manual. Enter your Nextcloud username, the app password and, as the server address, the address of your Nextcloud without https://, for example yourname.webokecloud.nl or cloud.yourcompany.nl. Click Sign In.

Not working with Manual? Then choose Advanced under Account Type and enter /remote.php/dav/principals/users/username/ as the Server Path (with your own username), port 443 and Use SSL checked.
Step 3: add your contacts
Open the Contacts app. Click Contacts in the menu bar at the top left and then Add Account...

Click Other Contacts Account...

Under Account Type, choose Manual and enter the same details as for the calendar: your username, the app password and the address of your Nextcloud. Click Sign In.

Done! Your calendars and contacts from your Nextcloud will now sync with your Mac.
Detailed explanation with screenshots: Calendar and contacts on the Mac in the Nextcloud manual. Nothing coming in? Read An app says "401" or keeps asking for your password.
