Give a new stepparent the same fair shot you’d want if you were the new one at the table.

Nobody at that table chose the situation, including them. A new adult walking into an established family is outnumbered, watched, and compared to somebody they cannot replace. You are allowed to be unhappy about how things changed and still not make them the target for it. Fairness here is not the same as warmth; you can be fair long before you feel anything.

Give it ordinary politeness and a little time. Find one thing to talk to them about that has nothing to do with the family, and let them talk. If it stays awkward, that is allowed, and your own parent is still the person to say that to.