At the moment you can still install the Ruby sass gem the usual way by following our instructions: Managing gems for your Rails applications
If you do, you'll see some warnings about the sass EOL, including this:
* If you use Sass as a command-line tool, we recommend using Dart Sass, the new
primary implementation: https://sass-lang.com/install
* If you use Sass as a plug-in for a Ruby web framework, we recommend using the
sassc gem: https://github.com/sass/sassc-ruby#readme
If you need the first option, the instructions there say:
You can install Sass on Windows, Mac, or Linux by downloading the package for your operating system from GitHub and adding it to your PATH. That’s all—there are no external dependencies and nothing else you need to install.
So, you can SSH to your shell user account and run the following to install the sass command-line tool:
mkdir -p ~/src
cd ~/src
wget https://github.com/sass/dart-sass/releases/download/1.26.2/dart-sass-1.26.2-linux-x64.tar.gz
tar zxf dart-sass-1.26.2-linux-x64.tar.gz
mv dart-sass-1.26.2-linux-x64/sass ~/bin/
If you need the second option, you can install the sassc gem as you would any other gem by using the instructions linked in the first paragraph of this reply.
