He exhaled. The file was correct. It was writing data to the correct memory addresses.

Typically ships with Android 7.1.2 or 10.1 (though often spoofed).

The blog Chinagadgetsreviews has maintained a firmware archive for MXQ boxes for nearly a decade. Search their site for "MXQ Pro 4K 5G S905X LP3 R29 V23 firmware". They usually provide Google Drive or MEGA links with MD5 checksums.