A Form 706 (estate tax return) does not have to be filed unless the estate is very large (i.e., exceeded $11.4 million for decedents dying in 2019).

See https://www.irs.gov/instructions/i706

The rent should be reported as income to the estate but deductions may be limited due to personal use, assuming the beneficiaries are the parties residing in the home and paying less than fair rental value.