If you are looking specifically for the GBA-exclusive dungeons and 2D sprite art, many gamers turn to emulation.
A script that stays closer to the original Japanese intent than the 1994 SNES release. Ways to Play Final Fantasy VI Advance 1. Official Digital Platforms (Recommended) Download Final Fantasy 6 Advance
Access to Leviathan, Gilgamesh, Cactuar, and Diabolos. If you are looking specifically for the GBA-exclusive