[arch-general] Plasma 5 - how to start afresh

Hello, I would like to restart the DE as if for the first time, and I don't know where the Plasma 5 user files are stored. There's no $HOME/.kde5 nor $HOME/.kf{,5}. Upon first start, the initial step was to localize the env to fr_FR. systemsettings crashed and/or hanged after choosing the relevant locale in all 4 existing tabs (translations, spell check, format, date time). After the third time I closed/restarted the session, the target locale finally prevailed. Not all strings are translated, I suppose a full l10n package will be avilable later on. So I wish to repeat the same steps, just to see if I run in the same crash/hang. Please advise how I can delete all kf5 settings ? Thanks.