Fulltextsearch/elasticsearch illegal argument exception

Hi,

I tried to setup fulltextsearch.
Setup:
Nextcloud: 23.0.3
Apache: 2.4
PHP: 7.4
Elasticsearch: 6.6.2 via Docker

occ fulltextsearch:test fails at Initializing index mapping with:

{"error":{"root_cause":[{"type":"illegal_argument_exception","reason":"requ
  est [/my_index] contains unrecognized parameter: [include_type_name]"}],"ty
  pe":"illegal_argument_exception","reason":"request [/my_index] contains unr
  ecognized parameter: [include_type_name]"},"status":400}

anyone knows what’s wrong here?

Elasticsearch v 6.17.2 works fine.