If you've got an A9LH system, what you could do is backup your NATIVE_FIRM folder to SD using Godmode9, rename it (put an A at the end or something), install the CIA, go back into Godmode9 and copy NATIVE_FIRM folder to SD again, rename it as well (put a B at the end for example), then rename the the original folder back, and copy it back over to restore the correct NATIVE_FIRM. Technically, the system should be unaffected by you replacing NATIVE_FIRM as long as you're not actually using CTRNAND NATIVE_FIRM, i.e. booting Luma without firmware.bin in place. I just suggested backing the folder up as a precaution. You should be able to restore the current NATIVE_FIRM via CIA. Anyway, once you're done, you should have a decrypted copy of the 9.0 NATIVE_FIRM in your SD card's 00000002B folder (or 20000002B folder if it's an N3DS). As usual, you should make a SysNAND backup first just in case anything goes wrong.