Save extraction and injection without CFW: Cybergadget, Japanese only, as you’ve mentioned.
one could use PowerSaves for extraction only back in the day (plus using a decryption software), but that ain’t exactly an option nowadays if I’m not mistaken.
Frankly, your go to is to hack your device. Any 3DS can be hacked. And the brick risk, while exists, is extremely extremely low, as long as you follow the instructions closely. I’ve hacked like 10 - 20 devices across the years (mine and others), using a myriad of different methods (through their stages of evolution). I know it isn’t a lot, but still, they all installed CFW safely.
I recommended ntrhax/magnethax (or whatever the cool kids call it nowadays), and it exploits a vulnerability in the hardware itself, so the loophole itself isn’t patchable by software revisions. It would require a magnet, and a DS flashcart tho.