You can set a default template for import using import profiles. There's more information on import profiles here: https://doc.laserfiche.com/laserfiche.documentation/11/userguide/en-us/Default.htm#../Subsystems/client_wa/Content/AddingContent/Import-Profiles.htm but essentially, it allows you to set up a collection of information about the document (including the template) that can be selected from a dropdown. If you have the Manage Repository Configuration privilege, you can also apply that profile to groups, including Everyone.

If you want a particular profile to be used by default by everyone, you'll next want to set an attribute on the Everyone group indicating that it should be used by default on all imported documents. To do so, navigate to the Everyone group in Repository Administration, go to the Attributes tab, and add a new attribute. Name it [Settings]DefaultImportProfile, and set the value to whatever you named your import profile.

With these two steps done, whenever a user imports a document, the template you specified in the import profile will be selected by default.

With that said, this just sets a default; a user could still change the template at the time of import. If you want to catch those situations, you could use a workflow similar to the one James Adamo mentioned.