Yes I will post here if I should hear anything back from Apple. Well the big hope is that we will get a new release latest next week with this hopefully being fixed. Let's keep fingers crossed.

I have seen the same behavior, my LG UltraFine 4K display just stays black and it is directly connected into the Mac Thunderbolt port. From what I have seen in other discussions, this seems to be limited to Intel based Macs and is a new bug in Beta 8 (M1 based Mac's seem not to have this problem). I have filed a bug report to Apple and hope they get it fixed as quickly as possible. It feels so strange to depend on the built in display and only have one display available and have the big black screen right in front of me. I had tried resetting NVRAM and SMC and no change, monitor still stays black. Also connecting original power supply is not making it work. Interestingly, USB devices connected to the monitor all work and the monitor shows up in the system report as connected to Thunderbolt / USB4 but it is not recognized as a Display device in the system report nor the system preferences. System preferences only has the internal display available.