To add further diverse coverage here on what has officially become AMD Radeon RX Vega Day, phoronix has an excellent write-up that covers the ins and outs RX Vega and Linux. Get your penguins ready my fellow neckbeards. Thanks cageymaru.
While the RX Vega performance on Linux may not be as good as some of you would have liked to see on day one, this is even now the fastest discrete GPU available with fully-open driver support. NVIDIA simply has no competition to provide when it comes to open-source driver support with their Maxwell/Pascal GPUs not even allowing re-clocking support, so they are limited to running at their boot clock frequencies, which is very slow.
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Source: [H]ardOCP – AMD Radeon RX Vega On Linux