You have different possibilities to work with composer package even if they are not in public repository like packagist.
1) Possibility
Own Composer Repository, you can achieve this with Satis or Private Packagist or Toran Proxy.
2) Possibility
Artifact, In this case you don't need have a online repository. Is a compressed folder with your private packages. E.g:
{
"repositories": [
{
"type": "artifact",
"url": "path/to/directory/with/zips/"
}
],
"require": {
"private-vendor-one/core": "15.6.2",
"private-vendor-two/connectivity": "*",
}
}
3) Possibility
Path You can specify a path (relative or absolute) of your composer repo in host. E.g:
{
"repositories": [
{
"type": "path",
"url": "../../packages/my-package"
}
],
"require": {
"private-vendor/package": "*"
}
}
With these possibilities you don't need deal with others solutions IMHO.
You have more info about composer repos here