Given that the project has been inactive for nearly a decade, it is unlikely a full patch will ever be released. The Hetalia fandom has largely moved on, and the technical difficulty of hacking DS visual novels (which use proprietary script compression) is high.
Several Hetalia fans have uploaded "subbed" playthroughs of the entire game. Search for "Gakuen Hetalia English Subtitle Playthrough." You won't be making the choices yourself, but you will experience the entire story and all the character routes with accurate English subtitles. Gakuen Hetalia Ds Rom English
Look at Reddit communities like r/roms or r/hetalia for verified, safe resources and setup guides. Given that the project has been inactive for
DeSmuME or MelonDS offer the highest compatibility and graphics scaling features. Search for "Gakuen Hetalia English Subtitle Playthrough
Some older DS translation patches suffer from memory overflow. Try switching from DeSmuME to MelonDS, as it handles memory emulation more accurately.
There is no official English localization planned by the original developers. How to Play in English
While the complete fan translation remains a holy grail for the Hetalia community, the quest has created a rich legacy of discussion, guides, and shared workarounds. In the meantime, the original Japanese game is out there, waiting to be explored, and learning a few key phrases might be the key to unlocking this fun and forgotten DS treasure.