We already covered this. There are no "indigenous Palestinian Arabs". No such thing. Completely fabricated propaganda.
So, when was it that the entire population of Palestine left and whole new bunch of immigrants moved in?
Can you give me a date?
When was it the entire population of any country left at the same time? Never.
Asking for something that doesn't exist is stupid.
But the lack of some magic specific date, doesn't prove the claim wrong either. Don't be an idiot.
There was no 'indigenous Palestinian Arabs' ever. That never existed. In fact, the name in itself is a contradiction. It's the same as saying the 'indigenous Crimean Russians', or the 'indigenous Ukrainian Russians'.
The only people indigenous today, to the land of Israel, is the Jews. Prior to the land of Israel, all the people groups with older claims, no longer exist. The people there now, that are not Jews, are immigrants.
At the very most, prior to the British control of the land, there are roughly 200,000 people that lived there, and some of them were Jews. The Ottoman empire ruined the land, with bad policies and lack of proper governance.
Most of the people that you claim are "Palestinians" are Egyptian. Some are Jordan, some are Iraqi, some are Lebanese.
But the majority are Egyptian. Some Egyptians fled to Israel (palestine), to avoid conscription. Deserters. Some were brought to Israel, as forced labor. When Egypt was rolled out of Israel by the Ottomans, many Egyptian soldiers deserted the army to stay in Israel.
The only group of non-jews that have been there for any real length of time, is the Bedouin tribes of Arabs. These showed up around the 7th Century. But to this day, the Bedouin tribes make up a tiny tiny fraction of the non-Jewish population. We're talking just a hundred thousand or so.
And quite frankly, if the only group to still be in Israel was the Bedouins, they would live at peace with Israel. Jews have been accommodating to the Bedouins, and the Bedouins (for the most part) have been accommodating to the Jews.
That isn't to say it's because they have a fondness for each other. Largely because the Bedouins have been nomadic herders for generations, and that doesn't conflict with the Jews.
Again, I'm not suggesting there are no examples of conflict between the two, only that largely they don't bother each other, as opposed to how Hamas and the IDF do.