When using the query for REST API (note you need to have curl installed:

MariaDB [test]> create table cusers3 engine=connect http='http://jsonplaceholder.typicode.com/users' table_type=json;

The result is:

• when used locally (VM Ubuntu Focal, MariaDB 10.6) , the result is:
  Query OK, 0 rows affected, 1 warning (0.140 sec)

  MariaDB [test]> show grants for current_user;

  +-----------------------------------------------------------------------------------------------------------------------------------------+

  | Grants for anel@localhost |

  +-----------------------------------------------------------------------------------------------------------------------------------------+

  | GRANT ALL PRIVILEGES ON *.* TO `anel`@`localhost` IDENTIFIED VIA mysql_native_password USING 'invalid' OR unix_socket WITH GRANT OPTION |

  +-----------------------------------------------------------------------------------------------------------------------------------------+

  1 row in set (0.000 sec)

  MariaDB [test]> show create table cusers3\G

  *************************** 1. row ***************************

  Table: cusers3

  Create Table: CREATE TABLE `cusers3` (

  `id` int(2) NOT NULL `JPATH`='$.id',

  `name` char(24) NOT NULL `JPATH`='$.name',

  `username` char(16) NOT NULL `JPATH`='$.username',

  `email` char(25) NOT NULL `JPATH`='$.email',

  `address_street` char(17) NOT NULL `JPATH`='$.address.street',

  `address_suite` char(9) NOT NULL `JPATH`='$.address.suite',

  `address_city` char(14) NOT NULL `JPATH`='$.address.city',

  `address_zipcode` char(10) NOT NULL `JPATH`='$.address.zipcode',

  `address_geo_lat` char(8) NOT NULL `JPATH`='$.address.geo.lat',

  `address_geo_lng` char(9) NOT NULL `JPATH`='$.address.geo.lng',

  `phone` char(21) NOT NULL `JPATH`='$.phone',

  `website` char(13) NOT NULL `JPATH`='$.website',

  `company_name` char(18) NOT NULL `JPATH`='$.company.name',

  `company_catchPhrase` char(40) NOT NULL `JPATH`='$.company.catchPhrase',

  `company_bs` char(36) NOT NULL `JPATH`='$.company.bs'

  ) ENGINE=CONNECT DEFAULT CHARSET=latin1 `TABLE_TYPE`='json' `HTTP`='http://jsonplaceholder.typicode.com/users'

  1 row in set (0.000 sec)

• in Docker is an error

  MariaDB [web_users]> create table cusers3 engine=connect http='http://jsonplaceholder.typicode.com/users' table_type=json;

  ERROR 1105 (HY000): Can only retrieve columns from object rows

  MariaDB [web_users]> select current_user;

  +----------------+

  | current_user |

  +----------------+

  | root@localhost |

  +----------------+

  MariaDB [web_users]> show grants for current_user;

  +----------------------------------------------------------------------------------------------------------------------------------------+

  | Grants for root@localhost |

  +----------------------------------------------------------------------------------------------------------------------------------------+

  | GRANT ALL PRIVILEGES ON *.* TO `root`@`localhost` IDENTIFIED BY PASSWORD '*EC427DF1E97E95DCB88D86BEDFE9AF58AE7D3563' WITH GRANT OPTION |

  | GRANT PROXY ON ''@'%' TO 'root'@'localhost' WITH GRANT OPTION |

  +----------------------------------------------------------------------------------------------------------------------------------------+

  The first thing CONNECT is doing is to create the file (in above example cusers.json, and from it is doing table discovery.
  In Docker file is created in data directory - /var/lib/mysql/web_users , directory that has file permissions of mysql:mysql.
  My testing involved different tests regarding curl versions (Ubuntu bionic default 7.58 and Focal default 7.68), hoping to get different types of files, but no, it is not curl related.
  I tested locally on Focal VM and it works, so my conclusion is that has something to do with Docker permissions.

• Docker container is started with:

  docker run -d -e MARIADB_USER=anel \

  -e MARIADB_PASSWORD=anel -e MARIADB_DATABASE=web_users \

  -e MARIADB_RANDOM_ROOT_PASSWORD=1 \

  -e MARIADB_ROOT_HOST=mariadb_server1 \

  -v $PWD/my_container_files:/etc/mysql/conf.d \

  --name mariadb-server1 \

  mariadb:latest

  where the config file in my_container_files/ dir is:

  printf "[mariadb]\nplugin-load-add=ha_connect\nplugin_dir=/usr/lib/mysql/plugin\n" >my_container.conf

  Haven't tested in other images but expecting to have the same behavior.