There is a threshold for being required to file an income tax return for an estate (gross income for the tax year of $600 or more).
See https://www.irs.gov/instructions/i1041#en_US_2021_publink1000285942
With respect to duties of a personal representative:
See https://www.irs.gov/publications/p559#en_US_2021_publink100099488
