Actually, there are multiple local phone manufacturers in the DPRK, including Arirang, Jindallae, and Phurun Hanal. They've all produced several original designs, and several phones have even been manufactured domestically. There's also a decently substantial clone market, which sells clones of smartphones popular in the west. A clone Samsung Note 8 and a clone of one of the iPhones somewhere in the 6-8 generation with virtually identical design come to mind as devices I've seen commonly in the hands of common people in and outside Pyongyang.

Devices can connect to the national intranet network called Kwangmyong via wifi or 3g data. There is in fact free public wifi in Pyongyang, with the SSID name "Mirae" or "future" and there's a streaming service that lets you watch live tv, domestically produced films, read newspapers, and even watch pirated foreign films.

Some access to the internet can be achieved, but the majority of the network's users are connecting via dial-up or their very heavily used 3g network which hasn't been upgraded substantially since the early 2000s due to sanctions. While there are hopes of moving the whole country to fiber, and there are terrestrial interconnects to the greater internet via China and Russia already built and in use. The intranet does have access to some external internet content, but the low power of most computers and low speed of the network means that modern websites are far too heavy to load, so services like reading world news or doing internet searches are achieved by domestic systems that scrape the web and then translate it into plain text and simple html only.