simply Google “DWI259S firmware download” and click the first link. Here is the official hierarchy of sources:

However, many users seek manual downloads to "unlock" the device from the eLife interface or to repurpose it after a subscription ends. 宽带技术网 How to Update or "Unlock" the DWI259S

You don’t manually download firmware for the Technicolor DWI259S. Keep the device online, reboot occasionally, and let your ISP manage updates automatically. If you have performance issues, the solution is almost never “find firmware online” – it’s contacting your provider.

Since official standalone firmware files are scarce, community-driven "unlock" methods are the most common way to modify the device's software: OTA Updates:

Create Bootable USB Drive for Etislat Dwi259s TV Box Android 9

To perform a hard reset (which might trigger an official update), hold the reset button (usually inside a small pinhole) while powering on the device to enter the Android recovery menu.