On startup of Quaternion I also see the following dialog box:
> Do you want to migrate the access token for @vendion:matrix.org from the file to the keychain?
Clicking "Yes" results in the following followup dialog box to appear:
> Quaternion couldn't save the access token to the keychain. Do you want to save the access token to file /home/vendion/.local/share/QMatrixClient/quaternion/@vendion_matrix.org?
Clicking "Yes" here then takes me to the login dialog box, after logging in the second dialog box appears saying that it couldn't save the access token to the keychain. I'm not sure if Quaternion is trying to save my access token (and credentials) to kwallet and failing or if something else is going on. I have other KDE/QT applications that is successfully able to access Kwallet without issue (kmail/kontact).
I have no idea what I have done locally, but when I start quaternion 0.0.9.4e it outputs this (among other things, and for multiple identities which I have):
Read the access token from the keychain for "@user:homeserver.org"
This is with quaternion running in a KDE Plasma environment, so I can't see what's different between your environment and mine.