I tried adding a Google Drive account in Dolphin but there was no entry for Google accounts. After reading another post, I installed kaccounts-providers which solved that. Now both in Dophin and KDE system settings, the Online account shows an enrty for Google. But when I click on it, I get the error message "There was an error while trying to process the request: Message recipient disconnected from message bus without replying."
Same error occurs when I chose OpenDesktop. But when I chose Owncloud and Nextcloud, a login window appears.
My suspicion is that it is trying to connect or start a browser but can't. Do I need to install anything else? I have both Firefox and Chrome installed.