Alright, so I’m definitely confused here.
I’m at the admin registration of the set-up, and it sends an email. Well, supposed to. Now, I set up SparkPost for my SMTP service, and that’s what I used to download Discourse with. Well, apparently I have to connect SparkPost with my domain, which is under construction (aka. it’s still on the “This domain has been registered. Check back later.” Well, SparkPost doesn’t ALLOW you to connect with those sites. So how am I supposed to confirm my email?
Have you asked Sparkpost?
No not yet. Should I?
Yep. 
Unless we’re misunderstanding you, the issue lies with Sparkpost and your DNS provider. It’s not Discourse related.
The first thing to do is to point the A record for your forum to your server. The rest you need to work out with sparkpost.
I’ve the same experience with Sparkpost and could not fully understand why.
My workaround, after half a day trying to review every logs/settings/feature in Sparkpost, tried with another email sending vendor, and it worked.
Try Mailgun, for example.