Made traditional IRA contribution for 2018 in 2019. Was I supposed to file 8606 form in 2019?

I am trying to properly file my ROTH conversion and found help in other discussions how to do it, but, apparently, I have a problem that was not addressed here (or, likely, just did not manage to find it).

In 2019 I made $6,000 contribution to traditional IRA. Fidelity "informed" me that I can make additional $5,500 contribution that will be counted as 2018 contribution. So, I went ahead and did it...

Now, when I file my 2019 return, I discovered that that $5,500, probably (as I understand it), should enter as "basis" since they ask only my 2019 contribution and 5,500 is "formally" 2018 contribution  (otherwise, TurboTax treat it as "excess" contribution). So, it looks like I was supposed to file 8606 form (looking at TurboTax help about that "basis" thing) as if I was supposed to know all those forms... (and as if IRS does not have all that info already...). I checked my Fidelity account and it does have properly filled 5498 form for 2019 (for 6,000 contribution) and for 2018 (for 5,500 contribution).

Do I understand the situation correctly? What do I do now? Go ahead and claim 5,500 basis now and fill late 8606 and pay the fine for late filing?

 

Thank you.