Unfortunately Amd stopped support of the Radeon cards for the Rx500/Vega series cards last year for Windows 8/8.1 as less than 2% worldwide used Win8 and only 6% used Win8.1 vrs @40% on Windows 7 and just over 50% on Windows 10. And those were last years numbers @July. Win7 is still second to Win10, but Win8 usage without free upgrade to 10 is more than likely less than 1% of Radeon users, with lower than 4% on 8.1 now. Figure a fraction of those users are using higher end cards. Probably done just to save money since there was so little need for the support of a half-baked OS.
My only advice is to try an older driver release for a Rx460, most driver updates are only for game optimizations anyways, that'll give you the basic drivers, but some of the more recent stuff found on the Rx5 series cards won't be available as long as you have Win 8.1, you'll need to move to Win 10 for full card support.