Paper Filed over a month ago and "Federal Return Pending"

Sorry--this will not be good news....

If you mail a tax return (or a payment) to the IRS, it is a good idea to use a mailing service that will track it like UPS or certified mail so you will know it was received.

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. 

Per the IRS website IRS Operations During COVID-19: Mission-critical functions continue: The IRS is not currently able to process individual paper tax returns. If you already have filed via paper but it has not yet been processed, do not file a second tax return or write to the IRS to inquire about the status of your return or your economic impact payment. Paper returns will be processed  once processing centers are able to reopen. 

TurboTax will not know anything about your mailed return, and will continue to show “Ready to Mail” on your account.  TurboTax will not know that you put your tax return in an envelope and took it to a mailbox.  TurboTax does not get updates on mailed  (or e-filed) returns.

When the IRS finally opens its mail and begins to process mailed returns you can check the status on the IRS site. https://www.irs.gov/refunds

State returns have to be mailed to the state.

https://ttlc.intuit.com/questions/1899433-how-do-i-track-my-state-refund

You say that you filed a 2018 return.  Since they are looking at returns for 2018 or 2019, they will be able to use your 2018 return to issue your stimulus check.