Unfortunately we have discovered a bug with AMD's OpenCL driver in the AMD Radeon RX 5000 series and above graphics cards. This has been reported to AMD, and while we wait on a solution, we have blocked these cards from enabling hardware acceleration. We hope this will be a temporary change, but unfortunately we can't give estimates on when it's likely to be fixed. There is no need to downgrade from 1.9.1 to 1.8.5, as the software-only performance will be the same between these two versions. Thanks for your patience.