Qubes-Whonix 14 / Qubes R4 DisposableVM support is mostly undocumented.
I suggest to modify Qubes Disposables according to the following plan:
- Whonix 13 DisposableVM: entirely unsupported
- Qubes R3.2 Whonix 14: entirely unsupported
- Qubes R4 Whonix 14: supported