So WildBill, I think we have a misunderstanding on how speed test works.
I will explain - feel free to skip parts in brackets which have more detailed explanations
You do not need a server in Adelaide to work out your Internet speed. (NBN equipment in Adelaide is probably aggregating traffic to data center in Melbourne - just my guess). This is what moderators are telling you.
I am mainly talking about the Ookla speed test web page - not the app.
When you load the speed test page, it automatically selects the best - that is the one that will show you the best result - server. (It does so based on a thing called "ping latency", which is right now, crazily bad at least for me indicating servers are overloaded. I suspect it is a current wider issue). On that page, you can choose any server, including in other countries (through settings).
The content you use when browsing is located all around the world, with very little hosted in Adelaide, so it makes no sense to measure speed to a server in Adelaide even if there was one.
So, when everything is working fine, the web page will find the best possible server (out of a list of well known servers) to give the best possible result (from ISP's point of view). For you it is probably the nearest Optus data centre which would be in Melbourne, but because it is not always Optus that is the "best latency server", you will often land on Telstra or Vodafone server (this fact just shows that their servers are not as overworked as Optus's).
(In fact I often measure speed to servers in US and Europe and even at best of times when my default server shows 55 Mbits/s, something in USA might be as slow as 10 or slower. This is most likely to do with ISP not buying enough capacity on inter-continental links. So when we say that our Internet is 55 Mbits/sec it is only true for content in Australia and is much slower to the rest of the world. Optus traffic goes through a different route than say Telstra's. Because of this bottleneck bigger firms providing streaming such as Netflix host their servers in Australia as well as all over the world.)
So, do not get hung up on a "pingable" server in Adelaide. You should be able to pick any server through settings on that page and check your Internet speed.
If your Internet connection is so bad, however, that the page can not even load properly (which is my case at the moment), you may end up under impression that you cannot do speed test at all.
And no need to have a go at me/others as not all of us are employed by Optus and just as stuck as you are.
Why couldn't someone (or your site) have told me this in the first place? What do you expect me to think when I get a variety of answers from different sources within Optus? Why do I get someone saying they don't know why I get Hobart or Melbourne etc? Why, when Optus asks me for photos of the speed tests on the App and the net to verify what I am unsure about, they say they can't explain it? "You should be getting Adelaide. Must be a fault somewhere. Try again later." How am I supposed to know that getting Telstra Adelaide or Hobart etc. speed test is maybe the closest to my Optus speed here? Why do providers say that they have the best speeds than others? How can it be proven? These are the sorts of things that don't make sense. I never said that my speed was too slow. Never queried that. I just wanted to know how I could check it. Simple question. What a frustrating waste of time this has caused me. I don't need another lecture. Don't tell me "no need to have a go at me/others .... and just as stuck as you are" What the?? I was told my case would be handed to an "expert." I'll leave it there. Maybe others on here who have the same issue can read this. Case closed.