QUIC can be enabled or disabled at three different levels. It's important to understand how these settings affect each other.
If QUIC is not explicitly turned off at any level, then priority for enabling QUIC is given at the most specific level: Virtual Host, then Listener, then Server.
If QUIC is explicity turned off at any level, then none of the more specific levels may turn it on. In other words, if QUIC is turned off at the Server level, then it cannot be turned on at the Listener level or at the Virtual Host level.
Put another way:
For a particular Virtual Host, QUIC will be ON
if:
ON
or is not set ANDON
or is not set ANDON
or is not set.
For a particular Virtual Host, QUIC will be OFF
if:
OFF
OROFF
OROFF
.