how to fly on elitras through baritone without fireworks if the cheat for flying on elytra is enabled

That's not intended usage.

Это непреднамеренное использование.

baritone/src/main/java/baritone/command/defaults/ElytraCommand.java

Line 131 in 93dee4f

gatekeep.append("Baritone Elytra is an experimental feature. It is only intended for long distance travel in the Nether using fireworks for vanilla boost. It will not work with any other mods (\"hacks\") for non-vanilla boost. ");

I found how to do it, you just need to change a couple of settings