Install rails 6.0 in Ubuntu 18

Step 1: remove ruby 2.5 because rails 6 needs ruby 2.6 and up

aptitude purge ruby

Step 2: install ruby

sudo snap install ruby --classic

Step 3: create a symbolic link in /usr/bin

sudo ln -s /snap/bin/ruby /usr/bin/ruby 

Step 4: install rails

sudo gem install rails -v 6.0.2.1 

Step 5: create a symbolic link for rails

sudo ln -s /home/leo2019/.gem/bin/rails /usr/bin/rails 

Step 6: verify

rails -v 

output: Rails 6.0.2.1