This has probably been mentioned but worth repeating and this is the highlight:
For 400 series chipset users ... the first beta BIOSes with Ryzen 5000 support to be made available from January.
"For 500 series chipset users, motherboards firmware that supports the new hardware should already be available. Users will need to ensure that a minimum AGESA version of 1.0.8.0 is installed which will ensure that the system will boot. For full support and performance, users should update to AGESA 1.1.0.0 for the best experience.
For 400 series chipset users, AMD is currently hard at work with motherboard partners to update their firmware stacks. AMD expects the first beta BIOSes with Ryzen 5000 support to be made available from January, however part of this will be motherboard manufacturer dependent. Full release BIOSes will be at a later date. When asked if the new 5000-series firmware for 400-series chipsets will remove support for older processors, AMD said it would be on a case-by-case basis depending on how the motherboard vendor wanted to enable support."
Source: Anandtech.