IDeviceInformation.cs

namespace MyApp.Helpers {
    public static class DeviceInformation {

        /// <summary>
        /// Finds out whether this is a low memory device using a Dependency Service
        /// </summary>
        [Preserve]
        public static bool LowMemoryDevice {
            get {
                var mem = DependencyService.Get<IMemoryHelper>().GetTotalMemory();
                mem = mem / (1000 * 1000);// To megabytes
                Debug.WriteLine($"Total Memory: {mem}MB");

                return mem < 500;
            }
        }
    }
}

MemoryHelper.cs

[assembly:Dependency(typeof(MemoryHelper))]
namespace MyApp.iOS.Helpers {
    [Preserve(AllMembers = true)]
    public class MemoryHelper : IMemoryHelper { 
        
        public MemoryHelper() { }

        public ulong GetTotalMemory() {
            return NSProcessInfo.ProcessInfo.PhysicalMemory;
        }
    }
}