The problem was that gpg-agent always stopped with the error message:

$ gpg-agent
gpg-agent[2857]: can't connect to `/home/schiesbn/.gnupg/S.gpg-agent': No such file or directory
gpg-agent: no gpg-agent running in this session

By default the gpg-agent on Fedora creates the socket in /tmp instead of in /home/schiesbn/.gnupg. So you have to move it manually over to your home directory once gpg-agent has started.

To do this I use this script:

#!/bin/bash
 
# Decide whether to start gpg-agent daemon.
# Create necessary symbolic link in $HOME/.gnupg/S.gpg-agent
 
SOCKET=S.gpg-agent
PIDOF=`pidof gpg-agent`
RETVAL=$?
 
if [ "$RETVAL" -eq 1 ]; then
	echo "Starting gpg-agent daemon."
	eval `gpg-agent --daemon `
else
	echo "Daemon gpg-agent already running."
fi
 
# Nasty way to find gpg-agent's socket file...
GPG_SOCKET_FILE=`find /tmp/gpg-* -name $SOCKET`
echo "Updating socket file link."
cp -fs $GPG_SOCKET_FILE $HOME/.gnupg/S.gpg-agent

To execute this script during log-in I have added this to my ~/.bashrc:

# GPG-AGENT stuff
GET_TTY=`tty`
export $GET_TTY
$HOME/bin/gpg-agent-start.sh

I still wonder why it works that easy on Debian and on Fedora i need all this scripting. But for the moment I’m just happy that I have found a solution to use my smartcard for SSH login on my Fedora systems.