Some languages such as Thai, Japanese, Chinese cannot use spaces as word wrapping boundaries.
Unity would have to integrate ICU4C to properly handle this.
In the meantime, an easy fix would be to respect the Zero Width Space Unicode character and treat them as normal white space that can be wrapped at.
TextMeshPro already does this, but Unity UI Text does not.
Then we can preprocess the input text with tools or plugins to insert the Zero Width Space characters.