Install old version from repository & rbenv :
sudo apt install ruby rbenv
Update ruby-build for rbenv :
git clone https://github.com/rbenv/ruby-build.git "$(rbenv root)"/plugins/ruby-build
git -C "$(rbenv root)"/plugins/ruby-build pull
Initialize rbenv and add the returned command to your ~/.bash_profile :
rbenv init
The command to add to your ~/.bash_profile :
eval "$(rbenv init -)"
Start a new console.
Update latest list of available versions if needed :
git -C "$(rbenv root)"/plugins/ruby-build pull
List all available versions :
rbenv install --list
Install a specific version (no YJIT) :
rbenv install [specific_version]
Install a specific version (with YJIT) :
apt install rustc
RUBY_CONFIGURE_OPTS="--enable-yjit" rbenv install [specific_version]
Set a specific version as the default for all consoles / everything / only the current directory :
rbenv shell [specific_version]
rbenv global [specific_version]
rbenv local [specific_version]