I am trying to upgrade an old 8.x site to 9.x and then 10.x.  It was originally installed via composer about 5 years ago.

The site is on Drupal 8.9.20 at the moment.  I have Composer 2.3.5, PHP 7.4.x, Apache 2.4.x, MySQL 5.7.x installed.  (I'm aware that these aren't supported any more.  I upgraded the OS and PHP went to 8.1.x and then the Drupal install broke.  I reverted to a VM snapshot and now I'm trying to update Drupal so it can run in newer PHP versions.  Once that is able to run in PHP 8.1 or higher, I'll update the OS, PHP, etc.)

A bit of context before I come to the question: When we build our site with composer install, we use a proxied repository instead of using Packagist and packages.drupal.org directly. This is a recommended approach to protect against Dependency Chain Abuse (Source: OWASP - "CICD-SEC-3: Dependency Chain Abuse"). One Drupal-Module we use has specified patches for a different module and for core in its composer.json file.

Hello,

I want to get my Drupal site up to date, at least to Drupal 9.4 that still supports php 7 Drupal 9.4 dropped official support for PHP 7.3, . 

I installed some modules via UI, so also want to install them with composer now, to get it all managed by composer.

When I go to do a simple

composer update

or

My Drupal site used to send me notifications for things like new account requests. At some point this broke, perhaps when going from 7 to 8. Now I want to fix it. I can see in the recent log messages that mail was sent,  but the recipient never received it, nor did I. 

Drupal 8.6.18

PHP 8.1.16 (I think)

Do I need to install the SMTP Authentication Support module? The doc page says it requires PHPMailer 6.x. 

My site is hosted at GoDaddy. Does that rule out using composer? How do I get to a shell command line? Do I just use manual installation through cPanel?