I had this problem on a friends very old PC just recently. I have quite a number of similarly old PCs and one with a near identical spec and all of these systems installed KB5016616 successfully.
My friend was anxious to get his PC back as quickly as possible as it's his main system. After a number of restores and checking logs etc, it was evident that KB5016616 was the culprit. Having done all the usual:
SFC /SCANNOW
DISM /ONLINE /CLEANUP-IMAGE /REVERTPENDINGACTIONS
DISM /ONLINE /CLEANUP-IMAGE /RESTOREIMAGE,
CHECKDISK /R /F
and a rebuild of the SOFTWAREDISTRIBUTION folder, any attempt to install KB5016616, either via Windows Update, or from downloading the update package, would result in a frozen boot and the spinning white dots. I imaged my friends system, stopped the windows update service on his machine and returned it to him, so at least he had a functioning system!
I restored his system's image to a spare hard drive and booted from my near identical system, so I could dig deeper and do some playing. All repositories and system files were error free and the system fully updated to pre KB5016616. Bespoke System Hardware Drivers were replaced with Microsoft defaults. MS Office was uninstalled as this had been mentioned as a potential issue and all Printer Drivers and associated software uninstalled. On installing KB5016616 and rebooting, the system froze with the spinning white dots.
The System is MBR not UEFI and does not have a 'Recovery Partition', but does have a 'System Reserved' partition. I expanded the 'System Reserved' partition and created a 'Recovery Partition', then established it via:
bootrec /rebuildbcd
reagentc.exe /enable
Previously, I rebuilt the MBR, Boot Record and BCD as follows:
bootsect /nt60 V: /force /mbr (V being the label of the 'System Reserved' partition establisked via DISKPART)
bcdboot C:\windows /s V: /f ALL
Unfortunately, this was to no avail and on installing KB5016616 and rebooting....well you guessed it!
I have a database for all PCs that I work on and the only differing factor from this system and my other equally as old systems, was that they were all fresh Windows 10 istalls and this particular one was a Windows 7 upgrade.
Doing a fresh install on my near identical system and installing the downloaded KB5016616 package was seemless and booted without issue.
I installed an old Windows 10 image (which was a Windows 7 upgrade) onto an old Dell laptop from which it was taken. On installing update KB5016616 and rebooting, the system froze at the spinning white dots. A fresh install had no issues.
Not that it helps much and hopefully Microsoft will fix this (as of typing 2022-08 Cumulative Update Preview for Windows 10 Version 21H2 for x64-based Systems KB5016688 has been released) but from my experience a system that has upgraded from Windows 7 has a problem!
I hope this helps someone.