GBARunner2
GBARunner2 is an open-source hypervisor that runs GBA games on DS/DSi/3DS in DS mode. It runs similar to Nintendont does for running GameCube games on Wii.
Along with what this wiki has to offer, the GBARunner compatibility lists have a lot of useful information:
Need help? Join our Discord server: DS⁽ⁱ⁾ Mode Hacking! (English only)