If your mother's estate was under the estate tax exemption amount ($12.92 million for 2023), then there will be no estate tax implications on the assets that were distributed.
If any of the assets, such as the house, were sold after her death, but before they were distributed, then her estate will need to file a 1041 tax return for estates and trusts, and K-1's will need to be issued to the beneficiaries. (This is not the same as the Form 706 Estate and Gift Tax return.)
Assets sold after they were distributed to the beneficiaries will be claimed on their personal returns. Basis in these assets will be stepped up to the fair market value at the date of her death.
IRA and pension distributions made directly to the beneficiaries will be taxable to them on at their normal rate. A 1099-R will get issued to them in these amounts.
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