I just ran into this as well. Pretty workflow breaking to be confined to only the laptop screen. I'm surprised (yet at the same time not surprised at all) that this would make it through to the official release. Hopefully a fix gets out soon...
My Setup:
macOS Big Sur v11.0.1
MacBook Pro (16", 2019) == TB3 ==> Plugable TBT3-UDZ == DP to HDMI ==> x2 ASUS VS238H-P
Monitors no longer detect any signal coming from MCB and the MBC is unable to detect monitors. I've gone through the whole array of standard troubleshooting steps; swap cables, test without dock, power cycle all the things in differing orders, etc.
123than
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Yup I ran into this as well. Been through all the troubleshooting with support with no luck. I'm really hoping this gets some visibility and a fix soon. Sucks trying to develop on just the laptop screen.