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