Noob Here: Question About Posting Content On Medium With Canonical Links

I am trying to rank for a very niche keyword. The search results on Google are filled with not relevant articles and also forum posts etc. This makes me feel like a great article that clearly answers the user's question is what Google is looking for.

Now, I just started my own blog on a new domain. So, I am sure that my blog would be in the Google sandbox for a few months (I hear 6 usually).

My Question:
If I post the article on Medium, I get the instant power of being on a great domain with a lot of authority. So, maybe Google will find my article and try it out in the SERPS.

BUT, if I post it with a "canonical" link to my sandboxed blog, I am not clear how Google will treat this.

Does it say:

• "Hey, the original article is not on Medium. It's on this blog. Really cannot show that blog. It's new and untrusted and in the sandbox"
• "Hey, cannot show the Medium link in the SERPs either. It's not the original article"

And because it cannot show the Medium article and the original article, it will show nothing.

Now, because of this, my article is getting no visibility. Which is silly.

So, is it better to just post the article on Medium without the canonical? At least I get the visibility that way?

(The big issue is TUST, however. Since, at the end of the day Medium could change its plans any time and say, "Hey all articles are behind a paywall" for example. For this reason, better to build a blog. But much slower to get out of the sandbox.)

Thank you for sharing your thoughts.