How to uninstall CFW? I have the latest Luma and an o3DS XL

if you mean removing a9lh, you have 2 options:
1. restore an old backup without a9lh installed, you can use decrypt9 and chose the restore option without "keep a9lh"
2. use SafeA9LHInstaller ((https://github.com/AuroraWright/SafeA9LHInstaller/releases). First make sure you dont have arm9loaderhax.bin placed in CTRNAND, you can check and delete it with fbi. Then copy the content of the zip file on your sd card and replace all files if necessary. When you start the 3ds press START to uninstall then press any button except SELECT and follow the instruction on the screen. I did this yesterday to remove a9lh and it worked for me.

 

i am glad it worked for you too