In the "Support" process, the notion "Product" is used by default to classify user requests. This scheme suits teams that support several software products within one support activity. You can easily change this terminology in the project Settings. For example, replace this term with "Service catalog" or some other classifier.
When the "products" (or services) reference list is very large, it becomes inconvenient to use. Moreover, some support projects have "products" and some do not. The problem is solved by selecting a request category first; the user is asked for it when creating a Request. A category is in fact the support project (activity) that the user selects first, and then creates a Request. In this case the Request creation form already shows the list of "products" of the selected project, or offers no choice if the "products" list is empty.
Because there are several support projects, it is convenient to manage them by creating a project Portfolio named "Support", in which Requests from all support projects are visible. On the shared request board you can not only see all support requests and their statuses, but also easily move requests from one category to another if the user did this incorrectly.