Deploying Angular app for different companies

I have an Angular app that we sell to different companies. The app is the same for all of them, except for a few differences among them.

Each one has a different Angular theme (a .scss file) and a specific configuration (which I managed to include in a different environment for each one).

So far, I created a configuration in the angular.json file replacing the default environment with the company's environment and the default theme with the company's theme as follows:

"COMPANY": {
  "fileReplacements": [
    {
      "replace": "src/environments/environment.ts", 
      "with": "src/environments/COMPANY.ts"
    },
    {
      "replace": "src/app/theme/theme.scss",
      "with": "src/app/theme/_COMPANY.scss"
    }
  ]
},

What I do to deploy into production is execute this command:

ng build -c COMPANY --prod --base-href "http://destination_url_of_the_app"

Then I copy the files in /dist into the server.

For the moment only the environment works, the theme is never replaced.

What is the best practice to achieve this? What am I doing wrong?

Thank you.