No – the TX3 Mini never had Widevine L1. It always streams Netflix at 480p. Custom firmware does not change this.
The Tanix TX3 Mini firmware is the software that controls the device's operating system, including the Android platform, and manages its hardware components. The firmware is responsible for booting up the device, loading the operating system, and configuring the various hardware components such as the CPU, memory, and storage. The Tanix TX3 Mini firmware is based on the Android operating system, which provides a user-friendly interface and supports a wide range of applications. tanix tx3 mini firmware
If you buy a Tanix TX3 Mini, take it out of the box, plug it in, and expect a polished, Netflix-ready experience, you are going to have a bad time. But if you buy it, plug it in, and immediately start looking for a screwdriver and a USB drive, you are in for a treat. No – the TX3 Mini never had Widevine L1