$dsn = 'select from config db table';
$db = new Connection($dsn);
$provider = new ActiveDataProvider([
       'db' => $db,
       'query' => Post::find(),
       'pagination' => [
          'pageSize' => 20,
       ],
]);

大概类似这样，你可以通过数据库配置表构造远程数据库的$dsn，然后构造一个Connection对象连接远程数据库，然后，将这个对象传给DataProvider即可。

    $connection = $apiweb->getDatabase($webid);
    
    $query = (new Query())->from('cm_category');   //这个地方可以用Post::find() 这样的方式来读取远程表吗？
    $dataProvider = new ActiveDataProvider([
        'db' => $connection,
        'query' => $query,
        'pagination' => [
            'pageSize' => 20,
        ]
    ]);

$dsn = 'select from config db table';
$db = new Connection($dsn);
$provider = new ActiveDataProvider([
       'db' => $db,
       'query' => Post::find(),
       'pagination' => [
          'pageSize' => 20,
       ],
]);

大概类似这样，你可以通过数据库配置表构造远程数据库的$dsn，然后构造一个Connection对象连接远程数据库，然后，将这个对象传给DataProvider即可。

可以类似这样处理。
main-local.php:

'components' => [
        'db' => [
            'class' => 'yii\db\Connection',
            'dsn' => 'mysql:host=192.168.80.1;dbname=test1;port=3306',
            'username' => 'root',
            'password' => '123456',
            'charset' => 'utf8',
        ],
		'db2' => [
			'class' => 'yii\db\Connection',
            'dsn' => 'mysql:host=192.168.80.1;dbname=test2;port=3306',
            'username' => 'root',
            'password' => '123456',
            'charset' => 'utf8',
		],

Model:

$connection = \Yii::$app->get ( "db" );
或
$connection = \Yii::$app->get ( "db2" );

可以类似这样处理。
main-local.php:

'components' => [
        'db' => [
            'class' => 'yii\db\Connection',
            'dsn' => 'mysql:host=192.168.80.1;dbname=test1;port=3306',
            'username' => 'root',
            'password' => '123456',
            'charset' => 'utf8',
        ],
		'db2' => [
			'class' => 'yii\db\Connection',
            'dsn' => 'mysql:host=192.168.80.1;dbname=test2;port=3306',
            'username' => 'root',
            'password' => '123456',
            'charset' => 'utf8',
		],

Model:

$connection = \Yii::$app->get ( "db" );
或
$connection = \Yii::$app->get ( "db2" );