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

[SET]

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.