Sorry i mean port 9090 and not 8090 
Port 8090 is required by YaCy, which also cannot be installed.
yunohost app install cockpit
Info: Installing cockpit…
Info: Provisioning system_user...
Info: Provisioning install_dir...
Info: Provisioning permissions...
Info: Provisioning ports...
Warning: Failed to provision ports : Port 9090 is already used by another process or app.
Info: Deprovisioning system_user...
Info: Deprovisioning install_dir...
Info: Deprovisioning permissions...
Info: Deprovisioning ports...
Error: Provisioning, deprovisioning, or updating resources for cockpit failed: Port 9090 is already used by another process or app.
https://paste.yunohost.org/raw/otugexicah
netstat -putlen | grep 9090
tcp6 0 0 :::9090 :::* LISTEN 0 19157 1/systemd