Как сделать, чтобы файлы офиса открывались программой Libreoffice

Решение первое (простое)

Удалить Р7 офис

su -
apt-get -y remove r7-office

Решение второе (сложное)

su -

if [ ! -f /etc/xdg/local/mimeapps.list ]; then
mkdir /etc/xdg/local
echo  'XDG_CONFIG_DIRS="/etc/xdg/local:$XDG_CONFIG_DIRS"' > /etc/profile.d/00-local.sh
chmod +x /etc/profile.d/00-local.sh
cp /etc/xdg/mos/mimeapps.list /etc/xdg/local/

sed -i '/^#.\+$/d'  /etc/xdg/local/mimeapps.list
sed -i 's/onlyoffice-desktopeditors.desktop;//g' /etc/xdg/local/mimeapps.list
sed -i 's/r7-office-desktopeditors.desktop;//g' /etc/xdg/local/mimeapps.list

sed -i '/^application\/vnd/  s/$/r7-office-desktopeditors.desktop;onlyoffice-desktopeditors.desktop;/' /etc/xdg/local/mimeapps.list
sed -i '/^text\/csv/  s/$/r7-office-desktopeditors.desktop;onlyoffice-desktopeditors.desktop;/' /etc/xdg/local/mimeapps.list
sed -i '/^application\/rtf/  s/$/r7-office-desktop;onlyoffice-desktopeditors.desktop;/' /etc/xdg/local/mimeapps.list
sed -i '/^application\/msword/  s/$/r7-office-desktop;onlyoffice-desktopeditors.desktop;/' /etc/xdg/local/mimeapps.list
fi