Thanks for the hint, but it didn’t help:
ufechner@tuxedo:~$ source ~/ros2_install/ros2-linux/setup.bash
ufechner@tuxedo:~$ talker
talker: error while loading shared libraries: librclcpp.so: cannot open shared object file: No such file or directory
ufechner@tuxedo:~$ locate librclcpp.so
/home/ufechner/ros2_install/ros2-linux/lib/librclcpp.so
ufechner@tuxedo:~$
The file librclcpp.so does exist, though.
Any more tips?