Posting to this thread as well to confirm and submit same issue as well:
I also have the same issue today immediately after upgrading from 6.8.0 to 6.8.1. The boot process hangs at the modprobe -r $DRIVERS command/step. It looks to be SAS related, but I'm no expert just see that was the step it seemed to be at. I can't even get the system to boot past this to try and roll back.
I'm running a Supermicro X9DRL-7F ATX Intel board which has an onboard LSI Broadcom 2208 SAS controller and I also have a Sun/Oracle F80 PCI Flash Accelerator card that I was using as SSD for cache, VM, Docker drive.
I have ECC 128G memory, and ran memtest, no errors as expected. In my opinion, highly unlikely to be memory since the error is exactly the same each time.
I have cloned the existing usb to another usb and tried to boot: same error
I have ran chkdsk and fsck on both usb's: there was some repairs, but same error
I have downloaded and flashed a new usb with clean unraid / no config: same error
Boot always dies saying with some sort of dump with last line being
/etc/rc.d/rc.M: line 164: 2363 Killed modprobe -r $DRIVERS
Edit 1: Tried to boot safe mode no GUI: same error
Edit 2: Copied the bz files from the /previous folder to root to restore the 6.8.0 version: successful boot on both usb's
Will try the renaming the 6.8.1 config/network-rules.cfg when I have time tomorrow to see if that fixes the 6.8.1 boot issue