It's my sincere hope that the items at the donation centers will find new owners for whom they will truly spark joy.

【翻译】我衷心希望捐赠中心的捐赠品能够找到新的主人，为他们带来真正的欢乐。

网友理解正确。that the items at the donation centers will find new owners for whom they will truly spark joy 是主语从句。

我把句子转换一下，就容易理解了：

That the items at the donation centers will find new owners for whom they will truly spark joy is my sincere hope.

然后，主表颠倒过来说：

My sincere hope is that the items at the donation centers will find new owners for whom they will truly spark joy.