After upgrading to v3.2.0 it is no longer possible to connect to pgbouncer, sql.Open returns:

ERROR: unsupported pkt type: 80 (SQLSTATE 08P01)

Here is a link to the configuration and open calls:
https://github.com/influxdata/telegraf/blob/03776088f135b040d8af93db4ee09f8bba1a5de7/plugins/inputs/postgresql/service.go#L112-L136

Git bisect indicates that it is caused by d9f21d0 overwriting the PreferSimpleProtocol in the pgx.ConnConfig.