i installed a new splunk enterprise server and configured it as deploy server as documented here:
then i added an app in $SPLUNK_HOME/etc/deployment-apps/MyApp
on the 26 forwarders running ubuntu 20.04 i ran splunk set deploy-poll MyDS:8089 but only 20 of them show up in the forwarder management.
when i remove one of them by clicking on "delete record", i can add a missing one by running splunk set deploy-poll MyDS:8089 again.
a license is installed too and it says 'DeployServer': 'ENABLED'
found the stupid mistake
the not showing forwarders where restarted and splunkd wasn't configured to start on boot 😞
unfortunately 'splunk set deploy-poll MyDS:8089' does not complain about not running splunkd.
anyway, changed config and all forwarders show up...
next issue probably coming soon 😉
Check if there is no connection issues from the missing UFs
You can use open ssl in CLI to test this from each UF host.
openssl s_client -connect MyDS:8089
If everything is fine you should see the details on the cert of your DS. If not, you might have something blocking the connection