If you have different users for different servers, don't use set :user. Encode the username into the server definition instead:

server "username@servername.tld", :app, :web, :cron, :db, :primary => true

Rails Long Term Support

Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)

Capistrano: Different usernames for each server