Configure the return_type field in ASP.NET Core

I'm using the AuthenticationBuilder.AddOAuth(...) method to add OAuth functionality to my site. This is working perfectly for one service I am connecting to, but the same doesn't go for the second service.

Apparently, during the redirect to the authorization endpoint, the second service requires the URL parameter return_type to be set to token, my configuration sets it to code though. I haven't been able to find what part of the OAuthOptions determines this parameter so far.

I'll add the code I am using for convenience:

authBuilder.AddOAuth(Identifier, options =>
{
    options.ClientId = ClientId;
    options.ClientSecret = ClientSecret;
    options.CallbackPath = new PathString($"/signin-{Identifier}");
    options.AccessDeniedPath = new PathString("/");
    
    options.AuthorizationEndpoint = Domain + AuthorizationEndpoint;
    options.TokenEndpoint = Domain + TokenEndpoint;
    options.UserInformationEndpoint = Domain + UserInfoEndpoint;

    options.ClaimActions.MapJsonKey(ClaimTypes.NameIdentifier, NameIdentifierKey);
    options.ClaimActions.MapJsonKey(ClaimTypes.Name, NameKey);

    options.SaveTokens = true;

    options.Events = new OAuthEvents
    {
        OnCreatingTicket = async context =>
        {
            var request = new HttpRequestMessage(HttpMethod.Get, context.Options.UserInformationEndpoint);
            request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
            request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", context.AccessToken);

            var response = await context.Backchannel.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, context.HttpContext.RequestAborted);
            response.EnsureSuccessStatusCode();

            var user = await JsonDocument.ParseAsync(await response.Content.ReadAsStreamAsync());

            context.RunClaimActions(user.RootElement);
        }
    };

    options.Scope.Add(Scope);
});