For the legitimate neon_1.49.0_armv8.apk :
The combination of ARMv8 (64-bit) and NEON (optimized instructions) ensures that your MX Player will handle 4K H.265/HEVC videos and surround soundtracks smoothly without overheating. 1.49.0 Armv8 Neon Codec Download For Mx
While MX Player itself isn’t on F-Droid, some F-Droid compatible repositories host the open-source components of the custom codec. This is a niche but secure method. For the legitimate neon_1