Update to kde-apps 18.12.3 ravaged my configs!?

[equaeghe]

Last night, I set the update of my plasma applications to 18.12.3 in motion. (It appears the old version has already been removed from the tree.)
This morning, the update was done, I had to etc-update two non-kde-related files, and I shut down my laptop. Now that I have restarted it, I get all kinds of problems: Trojita (a qt mail app) seems to have lost its configuration (it is now the default again), the wallet doesn't open automatically, authorized applications don't get access to the wallet, my desktop configuration is messed up (I had a auto-hide panel, it is now fixed), and the list goes on.

What has happened!?

I've never had this kind of breakage after a kde-related update in the last years. The fact that at least one configuration file was overwritten with the default is very worrying.

[EDIT] List of affected applications discovered:

• Trojita
  
• KMail
  
• Kile
  
• KSysGuard (lost some tabs)
  
• Plasma
  
• Zanshin
  
• akonadiconsole
  

And… my wallet file was replaced by an empty one!!!

(Everything I found to be replaced has been restored from backup.)