If you cannot find version 21.09 specifically, it is usually recommended to use the latest version available on the manufacturer's site (e.g., v22.x or higher), as these are backward compatible with older cards and include bug fixes.
For the most stable version and documentation, you can access downloads through these specialized technical platforms: hcled 21.09 led software download
Users can modify font styles, colors, moving character speeds, and specific playback schedules. If you cannot find version 21
No major brand (NovaStar, Linsn, ColorLight, Mooncell, Huidu, etc.) officially releases a product named exactly hcled 21.09 . v22.x or higher)