Kubuntu's live session suffers from https://bugs.kde.org/show_bug.cgi?id=387502, which is caused by not having a completely configured and provisioned KWallet.
Resolving the bug requires two things:
- Include the libpam-kwallet5 package
- Pre-provision KWallet with a wallet for the live session user, and that wallet's password needs to be the same as the live session user's password (or both can be passwordless, I suppose)
The live session already includes the libpam-kwallet5 package. Only the wallet part needs to be done now. Once that's complete, a major papercut in the live session will be resolved!