I got it working in shell as well:

#!/bin/bash

read -p "Username: " user
read -p "Password: " -s pass
read -p "TOTP: " totp

res=$(curl \
    --request POST \
    --url "https://feddit.ch/api/v3/user/login" \
    --header 'accept: application/json' \
    --header 'content-type: application/json' \
    --data '{"username_or_email":"'$user'","password":"'$pass'","totp_2fa_token":"'$totp'"}')

jwt=$(echo $res | sed -re 's/^.*"jwt":"([^"]*)".*$/\1/')

curl \
    --request GET \
    --url "https://feddit.ch/api/v3/user/export_settings" \
    --header 'accept: application/json' \
    --cookie "jwt=$jwt" \
    -o "export.json"

I'd recommend echoing $res and $jwt before processing them further

Edit: if you don't have TOTP enabled, don't forget to remove it from the request

Docs: https://lemmy.readme.io/reference/post_user-login

Edit 2: added spacing