Deserialize postgres jsonb to JObject

I have a table that has a jsonb column which I'd like to deserialize to a JObject (Newtonsoft.Json) or the equivalent API in System.Text.Json.

I am following this old issue which uses a SqlMapper:

https://github.com/DapperLib/Dapper/issues/719

But I get the following error:

fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1]
      An unhandled exception has occurred while executing the request.
      Npgsql.PostgresException (0x80004005): 42601: syntax error at or near "["
      
      POSITION: 15
         at Npgsql.Internal.NpgsqlConnector.<ReadMessage>g__ReadMessageLong|213_0(NpgsqlConnector connector, Boolean async, DataRowLoadingMode dataRowLoadingMode, Boolean readingNotifications, Boolean isReadingPrependedMessage)
         at Npgsql.NpgsqlDataReader.NextResult(Boolean async, Boolean isConsuming, CancellationToken cancellationToken)
         at Npgsql.NpgsqlDataReader.NextResult()
         at Npgsql.NpgsqlCommand.ExecuteReader(CommandBehavior behavior, Boolean async, CancellationToken cancellationToken)
         at Npgsql.NpgsqlCommand.ExecuteReader(CommandBehavior behavior, Boolean async, CancellationToken cancellationToken)
         at Npgsql.NpgsqlCommand.ExecuteReader(CommandBehavior behavior)
         at Npgsql.NpgsqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
         at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior)
         at Dapper.SqlMapper.ExecuteReaderWithFlagsFallback(IDbCommand cmd, Boolean wasClosed, CommandBehavior behavior) in /_/Dapper/SqlMapper.cs:line 1066
         at Dapper.SqlMapper.QueryImpl[T](IDbConnection cnn, CommandDefinition command, Type effectiveType)+MoveNext() in /_/Dapper/SqlMapper.cs:line 1094
         at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
         at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
         at Dapper.SqlMapper.Query[T](IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Boolean buffered, Nullable`1 commandTimeout, Nullable`1 commandType) in /_/Dapper/SqlMapper.cs:line 734
         at Dapper.Database`1.Query[T](String sql, Object param, Boolean buffered) in /_/Dapper.Rainbow/Database.cs:line 360
         at Dapper.Database`1.Table`2.All() in /_/Dapper.Rainbow/Database.cs:line 127
         at Program.<>c.<<Main>$>b__0_0()
         at lambda_method1(Closure , Object , HttpContext )
         at Microsoft.AspNetCore.Http.RequestDelegateFactory.<>c__DisplayClass36_0.<Create>b__0(HttpContext httpContext)
         at Microsoft.AspNetCore.Routing.EndpointMiddleware.Invoke(HttpContext httpContext)
      --- End of stack trace from previous location ---
         at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
         at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
        Exception data:
          Severity: ERROR
          SqlState: 42601
          MessageText: syntax error at or near "["
          Position: 15
          File: scan.l
          Line: 1180
          Routine: scanner_yyerror

Start by inspecting Dapper.Rainbow/Database.cs around the Table.All and Query call sites shown in the stack trace, then follow the generated command into SqlMapper.cs around lines 1066 and 1094. Reproduce the PostgreSQL jsonb-to-JObject query and determine what must change so the command executes without the syntax error and the value maps correctly.