Select X470 and B450 motherboards from ASRock and Gigabyte are already getting beta BIOS versions supporting the Ryzen 5000 CPUs with SAM function. MSI and Asus are also offering unofficial BIOS updates for testers. However, these are not stable versions by any means, so users are advised to wait for the official AGESA V2 1.1.0.0 BIOS releasing in January.
https://www.notebookcheck.net/AMD-Smart-Access-Memory-support-already-available-in-beta-form-for-select-X470-and-B450-motherboards-full-support-coming-in-January-2021.506447.0.html
The 27 people that actually managed to buy a RDNA2 card will be very happy about it!
And from those 27, the 10 that could get their hands on the Ryzen 5xxx are even happier since they don't have to wait until January for the official bios 😎