Red Viper's pretty slick, posted about it on March 6th after I'd installed it. They've made a number of improvements to the emulator since then, such as adding the ability to use the physical controls to navigate the file browser and running the 3DS's display at the Virtual Boy's 50 Hz refresh rate (which eliminates judder).
I'd already jailbroken my 3DS back in 2022 after learning about @wavemotion's awesome StellaDS emulator. It's for the DS, but runs just fine on the 3DS :
and A7800DS (Robotron plays great with the 4 buttons mapped as the second joystick):
I really like how he's used the 2nd display as the console interface. He has 7 emulators available on his GitHub page, the others are ColecoDS, NINTV-DS (Intellivision), DS994a, A8DS (Atari 8-bit computers), and A5200DS
One thing I found useful was to install an FTP server on the 3DS. That lets me add/update files to the SD card without having to remove the handles that block my SD card slot. I'd snapped those on as my hands would cramp without them. This reply in the StellaDS topic goes into the FTP server.
Wasn't aware of the Gameboy Advance games, will have to look into that. I did have a Gameboy Advance SP at one time, had to snap handles on it as well. I recall buying it to play a couple of Spyro the Dragon games(Season of Ice and Season of Flame). Don't have it anymore, think I gave it to one of my nephews.