A T-Mobile OnePlus 8 case won't fit Verizon's model, and 5G means no dual SIM support

Those $100 in savings come with strings attached, though, and by strings we mean you are likely to miss some, ahem, text messages and the like as the phone won't be registered as "C DMA-less" device on the billing's side at Verizon. 

Also, there are issues with the dual-SIM functionality of the 8-series which is locked in the US for now, but may be unleashed with an update further down the road. The biggest drama, however, is with cases.

It turns out that there are other, more mundane caveats to consider when buying a OnePlus 8 5G, especially Verizon's UW (Ultra Wideband) edition, too. The OnePlus 8 model at the manufacturer's website is cheaper than Verizon's with $100 for a reason. 

The Verizon version supports the carrier's 5G mmWave bands, and these need deliberate request from the phone maker and carrier to the modem maker to unleash the respective frequency filters, and to supply a bunch more antennas to place inside the phone.

This not only raises the cost of components that go into a 5G mmWave phone, but requires more testing and certification, increasing the price even further. For that reason, the unlocked OnePlus 8 wouldn't support Verizon or AT&T's 5G connectivity even if you manage to register it on their networks, as the Verizon-exclusive model has mmWave modem built in.

That same extra chip had to be affixed somewhere, and from the FCC schematics it seems that on Verizon's OnePlus 8 5G UW model, that place is right around the volume rocker. 

What does that mean for humanity? Well, that the volume key is shifted slightly down on Verizon's 5G UW version, hence the cheapo cases you ordered from Amazon for your precious, won't fit. The ones you get from T-Mobile won't work either. You are left with whatever is left on Verizon's store as a OnePlus 8 5G UW case, and users moan that those are either out of stock, expensive, or ugly. While the last argument is an acquired taste, it is something to keep in mind when getting Verizon's cheapest 5G mmWave phone this season.

Next in line for the OnePlus 8-series grievances in the US is that the phones, which are equipped with two SIM card slots, only have one activated in the initial firmware version. That's actually not at all surprising as these are 5G handsets, and modems that support 5G on both SIM card slots are few and far between from Huawei with its homebrew 5G chipset. 

The 5G model of our Oppo Find X2 Pro unit, for example, which is the inspiration for the OnePlus 8 Pro, has only one SIM slot active, even though it has two on the tray. The company's explanation was that it is a firmware issue, and if you want a dual SIM functionality, they'd have to preinstall the 4G model's factory firmware.

Something similar may be happening to the OnePlus 8-series in the US, too. Given that Verizon's OnePlus 8 5G UW model supports mmWave bands, it is hard to fathom how a second SIM card would offer the same functionality. 

Heck, Qualcomm's X55 modem that comes with Snapdragon 865 even has to be retooled with additional filters and antennas, just to support Verizon's Ultra Wideband network, let alone provide two simultaneous high-speed connections. 

That's probably coming with the next X65 edition at a later date, but in the meantime bear in mind that even the unlocked OnePlus 8 versions in the US are crippled when it comes to dual SIM functionality, at least for now, but there's hope for the future according to the OnePlus specification pages: