To install (currently installs version 1.22.10):
mkdir -p ~/src/yarn cd ~/src/yarn sudo apt install npm npm install yarn sudo ln -s "$PWD/node_modules/yarn/bin/yarnpkg" /usr/bin/yarnpkg
You should check that the SHA256 reported of the cli.js file is the same as the file dowloaded from https://yarnpkg.com/package/yarn?files:
wget https://cdn.jsdelivr.net/npm/yarn@1.22.10/lib/cli.js sha256sum cli.js node_modules/yarn/lib/cli.js defb0fe75a912a939852526658f6e7c09171c773f384e6add1c92a13112e0d0e cli.js defb0fe75a912a939852526658f6e7c09171c773f384e6add1c92a13112e0d0e node_modules/yarn/lib/cli.js rm cli.js
To upgrade:
cd ~/src/yarn yarnpkg upgrade