I have tried the same on my test machine and I don't see any issue while taking dump of the partitioned table, also command you have used is fine except -i option which is deprecated. Please confirm if you are not able to view data (after restore) in child tables or in parent table. Also you can try to take the dump of the one of the the partitioned table using -t option so that we can find out the exact issue. In normal scenario pg_dump works fine with the partitioned table.
Partition tables are empty in backup while using pg_dump to take backup, but the actual tables in database have data. Below is the command used to take backup.
