The mobile app and mobile web Wikipedia interfaces automatically pulls item descriptions from Wikidata, where an item description in the same language exists.
But when browsing the Cantonese Wikipedia using either mobile interfaces, the correct label cannot be extracted from Wikidata because the domain name (zh-yue.*) doesn't match the language code (yue). (The domain name vs ISO 639 discrepancy is discussed on T10217.) When trying to **edit** the Cantonese item descriptions using the mobile app, an error occurs because the app tries to find a non-existent language "zh-yue" on Wikidata.
Until T10217 gets fixed (it has already taken 9 years and is still open), please resolve this mismatch by letting zh-yue.wikipedia entries match up with the yue language descriptions on Wikidata for both reading and editing.