Alternatively, via XDA:
VLC has built-in ARMv7 NEON support, plays almost everything, and is completely free without ads. No codec hunting needed.
Downloading and installing the ARMv7 NEON codec for MX Player 11.3.0 is a straightforward process. Here's a step-by-step guide:
For version 1.13.0, you should use the corresponding custom codec pack. While official stores often push the latest version (currently 1.10.x - 2.7.x for modern MX Player), you can find the specific ARMv7 NEON file or the All-in-One (AIO) pack below: All-in-One (AIO) Pack: Download mx_aio.zip