The reason for this problem is that in a grid layout, the length of the label extends beyond the screen because there is no width limit.
Therefore, you only need to give the Label a length limit, such as
<Label WidthRequest="400" .../>, and you will find that the line break is working.
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Thanks for your feedback.
After testing, this issue may be caused by the
Layoutexceeding the screen width when reading
Therefore, it is more recommended to post your issue on MAUI issues to make our product group aware of it.