Using [FromUri] attribute - bind complex object with nested array

You can write a custom binder. This is for NET 9, but it should work for NET Core in general (I think).

Here's a sample of one I wrote for DataTables.Net, which submits GETs in a similar way...

This are my classes

public class DataTableRequest : IDataTableRequest
{
    public int? Draw { get; set; }
    public IEnumerable<Column>? Columns { get; set; }
    public IEnumerable<Order>? Order { get; set; }
    public int? Start { get; set; }
    public int? Length { get; set; }
    public ISearch? Search { get; set; }
    public Dictionary<string, string?>? OtherValues { get; set; }
}

public class Column : IColumn
{
    public string? Data { get; set; }
    public string? Name { get; set; }
    public bool? Searchable { get; set; }
    public bool? Orderable { get; set; }
    public Search? Search { get; set; }
}

public class Search : ISearch
{
    public string? Value { get; set; }
    public bool? Regex { get; set; }
}

public class Order : IOrder
{
    public int? Column { get; set; }
    public string? Dir { get; set; }
    public string? Name { get; set; }
}

And these are my binders

// DataTableRequestBinder.cs

using System.Text.RegularExpressions;
using CorreoNet.Web.Models.DataTablesNet;
using Microsoft.AspNetCore.Mvc.ModelBinding;

namespace CorreoNet.Web.Binders;

public class DataTableRequestBinder : IModelBinder
{
    public async Task BindModelAsync(ModelBindingContext bindingContext)
    {
        await Task.Delay(0);
        
        var request = bindingContext.HttpContext.Request;
        var values = bindingContext.ValueProvider;
        
        // initialize with the simple types
        var model = new DataTableRequest
        {
            Draw = int.TryParse(values.GetValue("draw").FirstValue, out var draw) ? draw : null,
            Start = int.TryParse(values.GetValue("start").FirstValue, out var start) ? start : null,
            Length = int.TryParse(values.GetValue("length").FirstValue, out var length) ? length : null,
            Columns = new List<Column>(),
            OtherValues = new Dictionary<string, string?>(),
        };
        
        // get columns
        if (values.ContainsPrefix("columns"))
        {
            var keys = request.Query.Keys.Where(k => k.StartsWith("columns[")).ToList();
            var colNumbers = keys.Select(k => Regex.Match(k, @"columns\[(\d+)\]").Groups[1].Value).Distinct().ToList();
            var columns = new List<Column>();
            
            foreach (var colNumber in colNumbers)
            {
                var column = new Column
                {
                    Data = values.GetValue($"columns[{colNumber}][data]").FirstValue,
                    Name = values.GetValue($"columns[{colNumber}][name]").FirstValue,
                    Searchable = bool.TryParse(values.GetValue($"columns[{colNumber}][searchable]").FirstValue, out var searchable) ? searchable : null,
                    Orderable = bool.TryParse(values.GetValue($"columns[{colNumber}][orderable]").FirstValue, out var orderable) ? orderable : null,
                    Search = new Search
                    {
                        Value = values.GetValue($"columns[{colNumber}][search][value]").FirstValue,
                        Regex = bool.TryParse(values.GetValue($"columns[{colNumber}][search][regex]").FirstValue, out var searchRegex) ? searchRegex : null,
                    }
                };
                
                columns.Add(column);
            }
            
            model.Columns = columns;
        }

        // get order
        if (values.ContainsPrefix("order"))
        {
            var keys = request.Query.Keys.Where(k => k.StartsWith("order[")).ToList();
            var colNumbers = keys.Select(k => Regex.Match(k, @"order\[(\d+)\]").Groups[1].Value).Distinct().ToList();
            var orders = new List<Order>();
            
            foreach (var colNumber in colNumbers)
            {
                var order = new Order
                {
                    Column = int.TryParse(values.GetValue($"order[{colNumber}][column]").FirstValue, out var column) ? column : null,
                    Dir = values.GetValue($"order[{colNumber}][dir]").FirstValue,
                    Name = values.GetValue($"order[{colNumber}][name]").FirstValue,
                };
                
                orders.Add(order);
            }
            
            model.Order = orders;
        }

        // get search
        if (values.ContainsPrefix("search"))
        {
            model.Search = new Search()
            {
                Value = values.GetValue("search[value]").FirstValue,
                Regex = bool.TryParse(values.GetValue("search[regex]").FirstValue, out var searchRegex) ? searchRegex : null,
            };
        }
        
        
        // get other keys
        var otherKeys = request.Query.Keys.Where(k => 
            !k.StartsWith("columns[") && 
            !k.StartsWith("draw") && 
            !k.StartsWith("order[") && 
            !k.StartsWith("search[") && 
            !k.StartsWith("start") && 
            !k.StartsWith("length")
        ).ToList();

        foreach (var key in otherKeys)
            model.OtherValues.Add(key, values.GetValue(key).FirstValue);       

        // bind!!!
        bindingContext.Result = ModelBindingResult.Success(model);
    }
}

and the provider, which you can add in your program.cs

// DataTableRequestBinderProvider.cs

using CorreoNet.Web.Models.DataTablesNet;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.ModelBinding.Binders;

namespace CorreoNet.Web.Binders;

public class DataTableRequestBinderProvider: IModelBinderProvider
{
    public IModelBinder? GetBinder(ModelBinderProviderContext context)
    {
        ArgumentNullException.ThrowIfNull(context);

        return (context.Metadata.ModelType == typeof(DataTableRequest)) ? 
            new BinderTypeModelBinder(typeof(DataTableRequestBinder)) : 
            null;
    }
}

I know it isn't exactly what you're looking for, but it did certainly helped me fix the same problem you have. Maybe it helps you a little bit.