Opensearch-dashboard anonymous access

I’ve installed opensearch and opensearch-dashboard. With security enabled it works well.
Now I would like to disable security and enable anonymous access.
What I already did:

opensearch.hosts: [http://localhost:9200]
/etc/opensearch/opensearch.yml true

opensearch-dashboards-plugin remove securityDashboards

and of course I restarted both services.

The query
shows me cluster is up.

But opensearch-dashboards is not accessible now. I got 502 Bad Gateway. Yes, opensearch-dashboards is behind revers-proxy (nginx). And all worked before I disabled security.
nginx logs:

failed (111: Connection refused) while connecting to upstream

I enabled logging.verbose: true on opensearch-dashboards configuration, but it didn’t show any errors.

How to properly enable anonymous access?

And one more question. How to install plugin to opensearch-dashboard after it was deleted.

opensearch-dashboards-plugin install securityDashboards
Attempting to transfer from
Plugin installation was unsuccessful due to error "No valid url specified."