Interesting. Firstly, the deadline to send a 1099-INT to the taxpayer is January 31. The fine for being late is $50 per form. You may want to contact the IRS.
Second, if you know the amount of interest that you were paid in 2017, you can report that interest without having the 1099-INT. Assuming you got the number close enough (+/- $5) then you would not need to amend when you get the form.
I invest with Acorns, which contacted me and told me that my 1099-DIV will not come until March 15th. (They received a waiver from the IRS) The rest of my taxes are complete, and I want to file as soon as possible, as I have been a part of Data Breaches from OPM (twice) Equifax, Blue Cross, Yahoo, and a couple of others, and I don't want someone to file a fraudulent return, and get my money. I earned less than $100 from Acorns and want to estimate the amount and file, but don't know what to put into TurboTax. Specifically, there are four boxes "Received from" which would be Acorns, Box 1a Total Ordinary Dividends, Box 1b Qualified Dividends, and Box 2a Total Capital Gains Dist. I think I put the estimated dividends in Box 1a, and leave the rest blank, but I am not sure.