Only time will tell if these rumors are true or not, but it's quite easy to put it to rest, if Netanyahu, is still alive let him come out on a live TV to deny thes allegations, that is if he has not done so already. I've seen pictures of him with a sixth finger where he was making a broadcast and some people are alleging that it was an AI doctored video and speech to deceive the public that he was still alive. If he's truly gone I don't see any reasons why the Israeli authorities will keep it a secret for this long, afterall nobody will live forever, keeping something like that a secret will give rise to more speculations which is not a good image for their country.
If Netanyahu is indeed killed, and he certainly is, then it is a war strategy for Israel to hide the news of his death. If the news of Netanyahu's death were to spread worldwide at this moment, it would psychologically demoralize the Israeli soldiers and the American soldiers, which is why they are keeping the news of his death a secret.
However, until Netanyahu comes on the live broadcast, the news of his death will remain a kind of fog for us. However, various media outlets have already reported his death multiple times, meaning that it may be at least partly true and he may have really died in the Iranian missile attack on March 11th.