he source has updated http://ppa.launchpad.net/ondrej/php/ubuntu/pool/main/x/xdebug/,so you get 404
edit file laradock/workspace/Dockerfile line 261apt-get install -y php${LARADOCK_PHP_VERSION}-xdebug && \
toapt-get update && apt-get install -y php${LARADOCK_PHP_VERSION}-xdebug && \
then run docker-compose build workspace