Composer, which is a must for drupal 8, 9 websites, is an application-level package manager PHP. I have developed tons of websites in drupal using composer. You can drop me a message if you want to develop your websites using composer any version including 1 & 2.
I am a native Drupal 9 developer with Core PHP OOP programming practical coding experience of about 12 years. I have developed a lot of custom modules in Drupal. I have developed numerous websites in Drupal CMS including E-commerce (Online Stores), Space booking engines, University sites, Sports, and many more using the commerce module and Ubercart module.
I have developed custom themes using the twig template structure of drupal 8/9 versions.
I can be your server manager including Linode which might be based on Linux/Ubuntu, using SSH shell commands with root-level access.