Assuming the living trust became irrevocable at the time of death (usually the case).

Assuming the stocks were in an account titled in the trust's name before death.

Then, if those assumptions are correct, at the time of death the trust received a stepped-up basis for those stocks owned by the trust.

If at some later time, the trust distributes the stocks in-kind directly to the beneficiaries of the trust, then the beneficiary's basis will be the same as the trust's basis (the stepped-up basis).

If instead, the trust sells the stock and then distributes the proceeds to the beneficiary, then when the trust sells the stock there will be either a loss or gain from the stepped-up basis. At the discretion of the trustee, and depending on what the trust document says about it if anything, the taxable gain or loss can either be declared on the trust's tax return or the tax liability can be transferred to the beneficiary (listed on the K-1 they receive from the trust).

You should confirm this with a CPA familiar with trusts. "Portfolio managers" are not always experts on either trusts or taxes.