On Kubuntu 20.04: When I enter my login password after a reboot - the KDE wallet gets opened during login and the wifi password (which is stored in the wallet) can be read by the wifi configuration. So all works as expected.
When I would like to use autologin and enable it, I get logged in automatically, but after the reboot the KDE wallet window appears and ask me to enter the user password. It is because KDE password wallet is still locked and wifi tries to read the password there. The only solution is to put the wifi password unencrypted for all computer users in the network settings. But this is a very bad solution to have an uncrypted password in the system. Why is it not possible to have both autologin and encrypted wifi password? I just can believe that is not possible/working in Kubuntu 20.04. Is there no way to achieve it?
If you want the password manager to automatically unlock, then you must sacrifice security. The only exception would be if you encrypted your entire Ubuntu installation. The obvious reason here is that you need to provide credentials to access encrypted protected information. If you want to skip that step, then you forfeit the protection it offers.
To answer your question: the way to automatically unlock
kwalletis to set the password to blank. Change the password and accept the new password making sure the password field is empty.