Duplicate applications for users with different database

I need to have a same reporting model and application with multiple reports, but each one should be fed with a local database, how would I do it this way?

Ex:
I have 3 X, Y and Z clients that have stores in the same branch, I need to create a base application that I will share with the 3 clients, but each application must use the client's local database through a gateway configured on the client machine, That is, each one owns a local system with its database with its releases, and each one must verify its data only.

I wanted to do it this way because I have multiple clients, and it's a very big job to redo each application with each client