I found a solution.
ASA does not add something to the HOSTNAME field to the Syslog HEADER if you don’t configure logging device-id <...> (which is RFC compliant but not realy advised)
When adding it you get a Syslog message that autoparse can parse
You can then use further extractors or pipelines to parse the Cisco tag.
2020-07-17T08:38:01+02:00 hostname : %ASA-3-711001: (...)