Awesome extension, although requires to install from source.

mkdir -p ~/.local/src/ffex
cd ~/.local/src/ffex
git clone https://github.com/nym-zone/block_cloudflare_mitm_fx.git
cd block_cloudflare_mitm_fx/src
zip -r -FS ../my-extension.zip * --exclude '*.git*'.
cd ..
mv my-extension.zip block-cuckflare.xpi

In LibreWolf and IceCat, you'll need to change 1 option (FireDragon and Iceweasel have it set to false by default):
about:config → xpinstall.signatures.required → false
Then install through the addon manager.

Also, FireDragon's default search engine is Cuckflared.