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The Trump phone just missed another release date
(www.theverge.com)
This is a most excellent place for technology news and articles.
I don't speak a dialect of English that uses that word but context clues tell me "tatty" means "the shittiest barely functional one electron away from being a brick phone fractions of a penny can buy".
It's also potatoes.
When I've heard "tatty," it's been short for "tattered." Like "threadbare." However, as you said, from context I assume that's not what's meant here.