Open this URL in your web browser:
https://<your-server-name>/info
The server will answer with a JSON String, which looks like this:
{"build":{"name":"metasfresh-webui-api","time":1554368261000,"version":"5.99.1-13675+master","jenkinsJobName":"metasfresh-webui/master","jenkinsBuildNo":"13675","group":"de.metas.ui.web","jenkinsBuildTag":"jenkins-metasfresh-webui-master-13675","artifact":"metasfresh-webui-api","jenkinsBuildUrl":"https://jenkins.metasfresh.com/job/metasfresh-webui/job/master/13675/"},"AD_System":{"implementationVersion":"5.99.1-10484+master","dbVersion":"5.99.1-14944+master"}}
You will find the version number after "dbVersion":. In this case it is the version 5.99.1-14944+master which is major ‘5.99’.
that version can be found on the server in this file:
/opt/metasfresh-webui-frontend/dist/info.json