To follow kovidgoyals tip to look into the calibre-server-logs i had to modify the service-file as i didn't had logging activated.
without logging:
ExecStart=/opt/calibre/calibre-server /home/store/CB --enable-local-write --userdb /home/store/CB/.config/calibre/server-users.sqlite --enable-auth --url-prefix /calibre --port 8080 --listen-on 127.0.0.1 --auth-mode "digest"
with logging:
ExecStart=/opt/calibre/calibre-server /home/store/CB --enable-local-write --userdb /home/store/CB/.config/calibre/server-users.sqlite --enable-auth --url-prefix /calibre --port 8080 --listen-on 127.0.0.1 --access-log /var/log/calibre/access.log --auth-mode "digest"
systemctl daemon-reload
systemctl restart calibre-server
Reloading the booklisting, the covers are showing up!
Then i disabled logging again, restarted calibre-server and the covers are showing up. Even with an other browser to exclude the browsercache, the covers are there.
I had to install xcb-util-cursor to get the calibre-client starting up. May this be the cause that the covers are shown now after restarting calibre-server?
Anyway,
mattmaria