According to official Serebii Patch History Logs , the key changes include:

In the digital preservation community, a or Region-Free tag means the game asset has been modified or compiled to bypass hardware region restrictions. This allows it to run seamlessly on any 3DS console running custom firmware, regardless of where the console was originally purchased. CIA (.cia)

If you are trying to from a physical cartridge?

A Nintendo 3DS, 3DS XL, 2DS, New 3DS, or New 3DS XL console.

: Multiple minor bugs were addressed to provide a smoother overall experience during exploration and battles.

This update was primarily released to maintain online compatibility and fix specific gameplay bugs:

Before attempting to apply the Update 1.5 patch, ensure your hardware or software environment meets these prerequisites: On Physical 3DS Hardware

The update file can be safely integrated into any regional variant of the game base.

A PC, Mac, or Android device running the latest stable build of Citra or its forks.