Ensure that the undub link you find matches your game's region (USA or EUR). Using a USA undub patch on a European version of the game can sometimes cause crashes or text alignment issues.
A great resource for finding updated links and installation guides. Searching for "Echoes undub" within this subreddit usually yields active MEGA or MediaFire links.
While primarily for vanilla content, some community-maintained repositories for homebrew 3DS consoles occasionally host pre-patched versions of the game. How to Install the Undub
If you have a 3DS with Luma3DS firmware, you don’t need to download a whole new game. You simply place the undub audio files in a specific folder on your SD card ( /luma/titles/[TitleID]/romfs ). The console then "layers" the Japanese audio over your English game disc or digital copy.