This is expected. This is a part of new hardening of Whonix Workstation templates and introduction of sysmaint
account. Here are more information on sysmaint
account.
To have sudo access to new Whonix Workstation (and Kicksecure) templates, open a terminal with sysmaint
account in them:
qvm-run -u sysmaint TEMPLATENAME xterm
or
qvm-run -u sysmaint TEMPLATENAME xfce4-terminal
Then you can use sudo