MacOS – Installing Big Sur Beta 5 on Catalina: stuck on black screen

betabig surbootmacos

Mac mini (late 2014)
macOS 10.15.6
running from a bootable microSD card (inserted into SDXC slot)
no firmware password
FileVault enabled (should be supported for install as of Beta 4)

Enrolled my Mac into the Public Beta program, downloaded macOS Big Sur Beta through Software Update (I do assume it downloaded the latest version i.e. Beta 5?), ran an update.

After a few hours updating, it stuck on “less than a minute remaining” for a good hour, then rebooted and hang up on the black screen with Apple logo. Diagnostics and Disk Utility’s First Aid find no issues. Rebooting in Safe Mode presents with a login window but gets stuck when progress bar reaches 100%. Clearing NVRAM and rebooting in Recovery mode leads to the same black Apple screen eventually.

I then rebooted in Verbose Mode. Terminal displayed many ‘failed to bootstrap path’ error notices, but nevertheless continued running the boot until it hang and resolved to black Apple screen.

Before switching to the black screen, it displayed the following:

setSystemTargetUUID will use / as the target
Found update container: LPAPFSContainer: AppleAPFSMedia
Found update container but did not find update volume. 
mountAndGetUpdateVolumeMountPoint defaultMountPoint failed to get defaultMountPoint
process_update_result_state: no update result file, assuming 1st boot after a restore
OSVersion changed. Notifying clients 
Attempting to cleanup saved RecoveryOS state. 
RecoveryOS status file not present(not an error)
RecoveryOS connectivity data file not present 
Clearing out RecoveryOS logarchives 
Deleting RecoveryOS logarchive files
Using default RecoveryOS logarchive preservation timeout

I thought issues with APFS containers were resolved in beta 5 release?

Resolved in macOS Big Sur 11 beta 5
APFS containers with non-default allocation block sizes are now supported for installation. (64312561)

Terminal then proceeds scheduling kernel threads. The very last lines before it hangs and switched to the black screen:

en2: promiscuous mode enable succeeded 
_dill_attach_flowswitch_nexus: en2 9000 1500 
en3: promiscuous mode enable succeeded 
_dill_attach_flowswitch_nexus: en3 9000 1500
IOConsoleUsers: time(0) 0->0, lin0, llk1,
IOConsoleUsers: gIOScreenLockState 3, hs 0, bs 0, now 0, sm 0x0
Got incomplete channel sequence length 0, should be 16
postMessage::1412 APPLE80211_M_BSSID_CHANGED received 
en1::IO80211Interface::postMessage bssid changed 
AirPort_BrcmNIC::getSSIDData(): Get failure: APPLE80211_IOC_SSID: 02

How can AirPort function be the one that breaks the boot? Do I read it correctly?

Any thoughts on what might have gone wrong?

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