mobile phone archos without an operating system

You can download the OS you prefer and install it by several possible methods, the least potential for things to go wrong involves finding the original manufacturer's stock ROM for your EXACT model. 'Close' isn't good enough, find an exact match, in your desired language. You may find ROMs, tutorials and tools at the following link. I'd try to find the ROM from the manufactuer's site instead for hopefully the most reliable source. Custom ROMS are also available, XDA is a good source for learning more. Of the searches I just did, the following link was the most helpful, again, I'd suggest you search for the Archos stock ROM on their official site if possible.

https://andr oidmtk.com/download-archos-stock-rom-models

Good luck. BE CERTAIN you understand the steps and have the needed software and tools before you start. A mistake can brick your device.