Stage 6 of in place upgrade 4.1 -> 4.2 failed

[apparatus]

Do you have some custom qrexec policies in dom0?
Maybe the upgrade script can’t convert some of your policies from old policy format to new policy format.

Qubes Upgrade to 4.2 - In Place Upgrade

You have an error in policy files somewhere. I’d suggest to remove all your custom policies and use all default policies for a test and if it’ll work then try to add your custom policies one by one. Related issues:

Comment from one of the linked github issues:

Summary of the problem: an ask rule with default_target= requires target=. If no target= is used, exception is thrown`, if it is used, only one qube can be selected.

An example of a problematic old policy rule:

Qubes Upgrade to 4.2 - In Place Upgrade

SOLUTION: In the directory /etc/qubes/policy.d 30-user.policy was modified as follows: qubes.Inputkeyboard * sys-usb @adminvm allow previously the policy was “ask default_target sys-gpu-gui” then changed to “sys-usb” then changed to “allow”