Bug#1059942: ssh-agent started in KDE session via systemd user sesson doesn't work without restart

Package: openssh-client
Version: 1:9.6p1-2
Severity: normal

Hi,

I must admit that's a weird one. I have a new notebook and decided not
to migrate my old installation but install anew. This made me end up
with KDE Plasma (intended) on Wayland (unintended). In this setup,
ssh-agent is started on login via system user session and doesn't work,
at least not with my Yubikey with PIV.

I can enter the PIN with ssh-add -t 7200 -c -s
/usr/lib/x86_64-linux-gnu/opensc-pkcs11.so. An incorrect PIN gets
rejected, so something correct is happening. ssh $HOST fails with "agent
refused".

I can start a new ssh-agent in a shell and use it - in this shell -
normally. And I can restart the session-based ssh-agent with systemctl
--user restart ssh-agent and that new instance works as well.

So there must be something different with the ssh-agent that gets
started on login.

I'm prepared to debug, just tell me what to do. I can live with an
occasional systemctl --user restart ssh-agent now that I know this
helps.

Greetings
Marc


-- System Information:
Debian Release: trixie/sid
  APT prefers stable-security
  APT policy: (500, 'stable-security'), (500, 'unstable'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 6.6.9-amd64 (SMP w/12 CPU threads; PREEMPT)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE=en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages openssh-client depends on:
ii  adduser           3.137
ii  libc6             2.37-13
ii  libedit2          3.1-20230828-1
ii  libfido2-1        1.14.0-1
ii  libgssapi-krb5-2  1.20.1-5
ii  libselinux1       3.5-1+b1
ii  libssl3           3.1.4-2
ii  passwd            1:4.13+dfsg1-3
ii  zlib1g            1:1.3.dfsg-3

Versions of packages openssh-client recommends:
ii  xauth  1:1.1.2-1

Versions of packages openssh-client suggests:
pn  keychain                   <none>
ii  ksshaskpass [ssh-askpass]  4:5.27.9-1
pn  libpam-ssh                 <none>
pn  monkeysphere               <none>

-- no debconf information