Thank you @Robert_Grantham for your quick response! I have installed libgnome-keyring-common using the above command. (The funny thing is, the package seahorse depends on gnome-keyring but not on libgnome-keyring-common.)
That seems to automatically store the password. (But I still cannot see an entry in Seahorse.) However, it still does not completely work as expected.
Now, when I start ownCloud, it still opens a browser tab and asks for authorisation. The difference is, I do not have to specify my password. (See images below.)
Is there any way to suppress this behaviour?
See second screenshot
Sorry, I am only allowed to upload one screenshot. The second screenshot just says: “The application was authorized successfully. You can now close this window.”
Edit: I have to back up a little bit. The password is only remembered until I log out of the Ubuntu session. So it remembers the password when restarting the program but not when restarting the PC.
Edit 2: Turns out, this is a Wayland problem. It works fine when using the X display server. For a workaround for Wayland, I had to run this command: export GSM_SKIP_SSH_AGENT_WORKAROUND=1 (source)
Sorry @Fresh_Dumbledore for taking over your thread. I was thinking we may be affected by the same bug. You said below that you already have all mentioned packages. But did you install gnome-keyring, or the KDE equivalent kwallet? See also here: github.com/frankosterfeld/qtkeychain/issues/45