SRS the UK stopped paying for the security (and yes it is from the public purse funded by ordinary British working people) only when Harry and Meghan had stepped down from being full working members of the Royal Family and had even moved away from the UK. Just as Prince Andrew's two princess daughters had their protection withdrawn a decade or so ago because they were thought to be not performing enough duties.

I am really baffled at why some non British people think us UK taxpayers should continue funding these incredibly wealthy people when they are no longer working members of the royal family?

I suppose grannie could have chosen to fund their security herself instead. After all her supposed favourite son, Andrew, now has no significant income other than his navy pension and is funded directly from his mother's personal income instead! But that one is down to her - not the people of the UK. And the Sussexes seem to have been careful not to criticise her at all. One would like to think it is because Harry truly loves his grannie but I imagine a "step too far" idea might be floating about somewhere too.