SUMMARY
Kmail fails to handle Gmail accounts

STEPS TO REPRODUCE
1. Add a Gmail account
2. Notice it doesn't work
3. 

OBSERVED RESULT
Under account settings, a "resource is broken" message is shown and the account does not appear under the list of accounts in the folder panel.

EXPECTED RESULT
Gmail was handled well until some months ago

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 5.2.18-200.fc30.x86_64
(available in About System)
KDE Plasma Version: 5.15.5
KDE Frameworks Version: 5.95
Qt Version: 5.12.5

ADDITIONAL INFORMATION
Notice that I've already tried doing almost anything including removing and re-adding the account, adding it manually, modifying settings manually, saving/not password.
Please, gmail compatibility is such a key feature for many of Us. I'm also sure this does not depend on OS version nor my machine, since I've upgrade from fc29 to 30 and nothing happens, moreover a friend of mine experiences exactly the same problem.
Previously on fc29, a "unable to open kwallet/retrieve password for this account" message used to appear.