Something like that probably:
> Sniggering Linux users who believe in open code and open standards can take a hike. The Online Accounts systems in GNOME, Ubuntu Unity, Plasma, and MATE do the exact same thing as Window 10
ouch. but to be fair you can configure carddav/caldav manually on linux (but well I didn't liked evolution so much, mutt is okish but only for text. well mac mail.app is worse since it can't send csv files correctly (it adds unnecessary lines into it depending on the encoding)) (and well gnome only supports 3 email providers with cal/contact sync in their boxes which is microsoft, google and exchange (you can also add generic smtp/imap of course but it's about caldav/carddav), and one can prolly use nextcloud for carddav/caldav sync which is supported in the box aswell)