I am not sure, if checking if Whonix-Workstation is running in an AppVM is useful.

Can you think of any situations, where it would make sense to configure Whonix-Workstation as a ProxyVM or NetVM?

- check if Qubes-Whonix-Gateway is running in the right type of VM (ProxyVM)
- report if Whonix-Workstation or TemplateVM is connected to netvm 'none'

https://github.com/Whonix/whonixcheck/commit/9949235e969a55e33f3098996a7440b6aabf0ffd

Can you think of any situations, where it would make sense to configure Whonix-Workstation as a ProxyVM or NetVM?

Is it supported by for example iptables settings? I think it's save to
treat such situation as an error.

marmarek (Marek Marczykowski-Górecki):

Can you think of any situations, where it would make sense to configure Whonix-Workstation as a ProxyVM or NetVM?

Is it supported by for example iptables settings?

Not at all.

I think it's save to
treat such situation as an error.

Agreed.

https://github.com/Whonix/whonixcheck/commit/877900240ce2f504d1892f078002954352aa576a