Copying prod multi-site installation to dev multi-site installation
I was able to get the current running prod version converted to use composer with out an issue.

If you have converted your site to use composer , you dont need to copy the whole code base into the new server. Just copy the config,custom modules, composer.json, composer lock files and other reqired files except the core, vendor and contributed modules into new server along with sites directory folder and run composer install in the root directory of the server.This can be done by initiating a git repo in the current code and using the default .gitignore file which is available in code.And cloning the same repo in new server.
As you have already copied all the files into new server.
Just run rm -Rf vendor , rm -Rf web/core and rm -Rf web/modules/contrib and run composer install from the root directory in the new server.
After doing this you will probably get your site running in Dev environment as well.