As of this update, kwalletmanager no longer stores any passwords, and has mysteriously also forgotten about the ones that were already stored.
It is also not possible to authorize any applications that may use the wallet. This was already the case since the previous update to kf6, but at least it did still remember the stored passwords then. Right now it’s useless, and I have to manually authenticate every time I start kmail. I even had to manually log into the forum — it’s a good thing I still remembered the password.