Following ASRock, ASUS has become the second OEM to launch the beta BIOSes supporting the newly launched Ryzen 5000 CPUs on the 400 series boards. The company has released the ComboAM4v2 188.8.131.52 BIOS which supports the Zen 3 chips, albeit there may still be some bugs or instabilities. However, the fact that the update is official says a lot.
AMD had initially promised support for the Ryzen 5000 parts on the B450 and X470 parts sometime in January 2020, but most board partners have already started working on the update, with a tentative release in December. ASRock and ASUS are the two OEMs to have already released the beta BIOSes well ahead of the specified time frame.