Multi vendor products, single store? How can I create products in Drupal8 eCommerce, which are from different vendors, but I'm handling it trough a single store ?
(Vendors should be invisible to the end customer).

I want in addition to keep track internally (for my own accounting purposes) which item from which vendor was sold, so I can reimburse the specific vendor.
Is there a way to put/attach "out-of-bound" info to products and eventually orders ?

I'm still in research phase, experimenting with Drupal. Is such thing possible ?
Yes it is. In the end even unlimited with custom code ..

To easily limit the access for a vendor to only his products, each one would need one or more product types, then you can apply the right permissions. Also I would add the vendor/user as a reference (field) to that product type.

There very good shipping methods, applicable for different countries etc.