Installed the "2020-05-27 Fix DPI issue - BETA" version of the EEPROM today - I've been trying out the previous betas throughout the last week and weekend.
Before that I had (obviously) updated all possible packages and ran 'sudo rpi-update' + rebooted. After running rpi-eeprom-update with the beta bin from yesterday (05-27-2020), I no longer get the "pre-boot" screen that was in the earlier beta (the one with the QR code on the upright corner.)
Instead, I get the basic rainbow screen IF there is a MicroSD card in the slot. If I try plugging the RPi4B in without a MicroSD card in the slot, or with a bootable USB media in either of the USB ports, I get a black screen and that's all -- according to the LED's, there's not even any disk utilization.
I don't know if this is an intended "feature" or not, but at least in my case it makes the troubleshooting of any possible early-on boot process problems a lot more difficult than what they were.
My MicroSD build still works though, and its Raspbian kernel is now at 5.4.42-v8+. Haven't observed problems in running that. Too bad the USB boot now doesn't seem to work at all.