Gmail Account cannot be accessed from KMail.
Login to Google account from Chrome
Visit Google’s supporting page for less secure apps
Select: Turn on Access for less secure apps
Even updating KMail, and from which re-login the google account does not solve the issue
Not just KMail in OpenSuse is considered as less secure apps, some copiers with scanner function and SMTP setting for email out scanned documents like Konica C554e copier are considered by Google as less secure apps (devices)!