TL;DR: After a few weeks of deliberation, AMD has solved the intermittent USB connectivity problem as reported by many users. An AGESA update containing the fix will be sent to motherboard manufacturers next week, and it will be up to them from there. AMD estimates that the first beta BIOS with the fix will be available in early April.
Reports of sudden USB disconnections and poor signal quality on AMD X570 and B550 motherboards starting becoming commonplace on Reddit at the end of last year. Three weeks ago, AMD finally acknowledged the problem and began collecting information from the afflicted. The severity of the problem was shown to fluctuate randomly, but the likelihood of its occurrence was correlated with taxing hardware like new GPUs and VR headsets.
AMD hasn't stated what the problem was unfortunately, but one Redditor suggests that the cause could be a "timing issue trying to synchronize USB signaling with the faster symbol rates of PCIe 4.0," while another thinks it might be caused by "a controller reset triggered due to too many uncorrectable PCIe errors."
Given that Redditors found a workaround that was good enough for AMD to recommend, their comments shouldn't be quickly dismissed.
Updated AGESA Coming for Intermittent USB Connectivity from r/Amd
If you've experienced the problem, put a reminder in your calendar for next month to check for an updated BIOS from your motherboard's manufacturer.