C# code for disabling minimizing, maximizing and resizing of console Window. Works on Windows, didn't check other systems.

DisableConsoleResize.cs

/*
    Code based on:
    https://stackoverflow.com/a/34199784/1816426
    https://stackoverflow.com/a/38175919/1816426
*/

class Program
{
    // Documentation: https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-deletemenu
    private const int MF_BYCOMMAND = 0x00000000;
    
    // Documentation: https://docs.microsoft.com/en-us/windows/win32/menurc/wm-syscommand
    public const int SC_SIZE = 0xF000;
    public const int SC_MINIMIZE = 0xF020;
    public const int SC_MAXIMIZE = 0xF030;
    
    // Documentation: https://docs.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.dllimportattribute?view=netcore-3.1
    [DllImport("user32.dll")]
    // Documentation: https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-deletemenu
    public static extern int DeleteMenu(IntPtr hMenu, int nPosition, int wFlags);

    [DllImport("user32.dll")]
    // Documentation: https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getsystemmenu
    private static extern IntPtr GetSystemMenu(IntPtr hWnd, bool bRevert);

    [DllImport("kernel32.dll", ExactSpelling = true)]
    // Documentation: https://docs.microsoft.com/en-us/windows/console/getconsolewindow
    private static extern IntPtr GetConsoleWindow();

    static void Main(string[] args)
    {
        DeleteMenu(GetSystemMenu(GetConsoleWindow(), false), SC_SIZE, MF_BYCOMMAND);        // Disable resizing
        DeleteMenu(GetSystemMenu(GetConsoleWindow(), false), SC_MINIMIZE, MF_BYCOMMAND);    // Disable minimizing
        DeleteMenu(GetSystemMenu(GetConsoleWindow(), false), SC_MAXIMIZE, MF_BYCOMMAND);    // Disable maximizing
        Console.ReadKey(true);
    }

}