Just create the file ~/.vimrc with the content set "mouse=":
Insert in ~/.vimrc:
vi ~/.vimrc set mouse=
Make it take effect
source ~/.vimrc
You can now select text with the mouse in Debian 9.
From: https://unix.stackexchange.com/questions/318824/vim-cutpaste-not-working-in-stretch-debian-9/387776#387776
