debezium could not access file "decoderbufs" using postgres 11 with default plugin pgoutput

You haven't set "plugin.name" property to "pgoutput" in your Debezium connector properties which you've already figured out. But this answer is for others who don't know where to set this option and for more clarity.

In the following connector properties:

As you haven't set plugin.name option it is taking the default value which is decoderbufs and that's why you were getting the following error:

Setting the "plugin.name" explicitly to "pgoutput" should solve the issue.

{ 
  "connector.class": "io.debezium.connector.postgresql.PostgresConnector", 
  "database.user": "postgres",
  "database.dbname": "xxxxx",
  "tasks.max": "1", 
  "database.hostname": "xxxx.rds.amazonaws.com", 
  "database.password": "xxxx", 
  "database.server.name": "database-1",
  "database.port": "5432",
  "plugin.name": "pgoutput" --> this property
}