Is a Postgresql Paroni cluster backup supported under CV, howto configure, howto Backup?

My customer setup a Postgresql Patroni cluster. I found this description

 Patroni : Setting up a highly available PostgreSQL Cluster - CYBERTEC (cybertec-postgresql.com)

If he backup one of the passiv nodes he got “Could not put the Cluster in backup mode”

PostGresBackupParent.log

AnalyzeResult() - eRRoR --  PQresultStatus indicates failure for SELECT pg_start_backup('name'). Error:ERROR:  recovery is in progress

I would say it is the nature of a “not master” node to be in recovery status.

Backup of master node cause no issues.

I found no document in BOL how to configure a patroni cluster or howto backup it.

Is it supported?