/usr/lib/ubiquity/target-config/31brltty is in brltty 5.5-4ubuntu2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 | #! /bin/sh
set -e
if egrep -q 'braille=ask|brltty' /proc/cmdline && [ -f /etc/brltty.conf ]; then
	if [ -e /target/etc/brltty.conf ]; then
		mv /target/etc/brltty.conf /target/etc/brltty.conf.orig
	fi
	cp -a /etc/brltty.conf /target/etc/brltty.conf
	chroot /target systemctl enable brltty
fi
exit 0
 |