Yes, it is an interference engine. Gates doesnt show it because they only show ones with a timing belt, and not timing chains as yours as. Below is from service manual:
They dont have an all inclusive listing. I have seen many vehicles with inteference engines not listed on the AERA listing.
The upload I sent you is from the SERVICE MANUAL. It is an interference engine, and I can attest to having seen bent valves from the altima 2.4L engine when the timing chain jumped timing, in one case actually put holes in the the pistons.
I cannot address why AERA doesnt list every vehicle that has an interference engine as I dont publish it an am not a part of their research group that gathers information. you would need to write AERA on why their list is not inclusive of all vehicles with interference engines.
Your question was whether the 98 Altima 2.4L is an interference engine. Yes, it is. I have even provided you with proof from NISSAN SERVICE MANUAL.