Regarding this old entry: Yarn: error: no such option: --pure-lockfile
That’s not a Debian issue, but a “problem” with the manual. Following the installation instructions is not enought, as it is not completely detailed. To avoid that problem in section Yarn, after:
echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list
You should run:
apt-get update && apt-get install -y yarn
You should have made the same previously with the nodejs package. In that case, indicate the version. So, in section Nodejs, after:
curl -sL https://deb.nodesource.com/setup_12.x | bash -
you have to enter:
apt-get install -y nodejs=12*
You do not need to update the apt cache because curl | bash does it for you. Otherwise, precede with apt-get update.
Hope it helps.