I have had the "watchdog" kernel panic issue when connected to an external LG Ultrawide. Whenever my MacBook Pro (15" 2018) would go into sleep when the LG Ultrawide was connected (Thunderbolt 3 -> Thunderbolt 2) the Mac would reboot and show the watchdog error.
The issue started with Catalina and remained for all Big Sur betas until RC1.
The issue is now fixed for me since RC1, and hasn't occured in RC2 either.
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I've also had customers with similar issues.
1 customer fixed it by replacing a video adapter (USB-C to Displayport)
Another customer fixed it by replacing an external HDD (Western Digital) that produced the issue.
It is worth noting that kernel panics (with or without the watchdog error) mentioned in this thread don't necessarily have the same problem source. For some it might be a peripheral issue, for some it might be a hardware issue, for some it might just be software (or a combination of software and peripheral). If you have the issue, do extensive troubleshooting via updates and temporarily removing peripherals. Don't blindly assume a hardware defect on your device.
The issue started with Catalina and remained for all Big Sur betas until RC1.
The issue is now fixed for me since RC1, and hasn't occured in RC2 either.
--
I've also had customers with similar issues.
1 customer fixed it by replacing a video adapter (USB-C to Displayport)
Another customer fixed it by replacing an external HDD (Western Digital) that produced the issue.
It is worth noting that kernel panics (with or without the watchdog error) mentioned in this thread don't necessarily have the same problem source. For some it might be a peripheral issue, for some it might be a hardware issue, for some it might just be software (or a combination of software and peripheral). If you have the issue, do extensive troubleshooting via updates and temporarily removing peripherals. Don't blindly assume a hardware defect on your device.