Mortgage interest, at best, is an itemized deduction. If you already don't make enough to have tax liability (before withholding), or if you don't have itemized deductions in excess of your standard deduction, there's no need to pursue mortgage interest as you won't get anything back from it.
In some cases (mainly disability retirement if you're under the plan's "minimum retirement age"), your disability income may be treated as "earned income" and qualify you for EITC. If so, you need to file a return to claim that credit. (The mandatory delay for EITC returns to at least Feb. 15 isn't that big a deal this year as it only extends 3 days beyond the announced IRS delay to Feb. 12 for processing ALL returns.) If you have other withholding or refundable credits (basically free money from the IRS) to claim, you'll need to file a tax return to claim those even if you're not required to file.
Finally, THIS year you may want to consider filing anyway (or using the forthcoming 2021 IRS "non-filer portal") to assure you get the maximum EIP (stimulus) checks you're entitled to for both 2020 & 2021. If you're not filing taxes, didn't use the 2020 "non-filer portal", and don't get Social Security (including SSDI), RRB, SSI or VA benefits, you may not have received the EIP1 ($1,200 per taxpayer + $500 per child under 17) or EIP2 ($600 per taxpayer + $600 per child under 17) checks this past year; even if you get a qualifying Federal benefit you may not have received the child enhancements. If any of these are the case, you should file to claim the Recovery Rebate Credit which makes up for the EIPs you were entitled to but didn't receive. Also, filing now (whether thru TurboTax or the 2021 "non-filer portal") will get you on the list for any future 2021 EIPs, such as the additional EIP President Biden has proposed for Congress to consider ($1,400 per taxpayer + $1,400 per child under 17, plus more for dependents who didn't qualify for EIP1 or EIP2).
