If you put Australia in the title, than any Ozzie who follows this forum will read/respond, so you are reaching the people who you want to reach.
The bigger question is whether it makes sense to organize the Purism forum according to regions, and I don’t think that it does. There have been 10 threads out of a total of 3199 threads with “Australia” in the title, so there isn’t that much need for the new category.
For the majority of topics discussed on this forum, they are not regional in focus. Occasionally there are questions about power plugs, taxes, shipping or cellular networks in a particular region, but most questions are worldwide in nature. For most people reading this forum, they want info on a product category (Librem laptops, Librem 5, Librem Mini). For example, if a question gets asked about the Mini in the “Australia” category, people who are interested in the Mini, are less likely to bother reading the topic, because they will assume that it only deals with Australian issues, so you are probably not going to get as good of responses because you get fewer readers.
Another problem is that you are basically asking Purism to double the number of available categories (there are currently 11), and then everyone will be wondering which category to use when creating a new thread. For example, if you have questions about the Librem 5 and cellular networks in a region. Some people are going to file the question under “Librem 5” and others are going to file under the regional category, and there will be no consistency.
If Discourse used a label system rather than categories, your proposal would make more sense, because people can select both an “Librem 5” and an “Australia” label, but if we have to decide between either filing under a product category or region, product category makes more sense to me.