Chromium has a lot of interesting settings (originally aimed for enterprise policies) here: https://www.chromium.org/administrators/policy-list-3#ImagesBlockedForUrls

At least some of them seem to be in chromium/components/content_settings/core/common/pref_names.cc so I guess could be exposed to Qt - there seems to be some interesting stuff there, like kManagedCookiesAllowedForUrls.

Another question would be if QtWebEngine should pick up system wide configurations from Chromium too, see e.g. https://www.chromium.org/administrators/linux-quick-start

Note that the page says:

These policies are strictly intended to be used to configure instances of Google Chrome internal to your organization. Use of these policies outside of your organization (for example, in a publicly distributed program) is considered malware and will likely be labeled as malware by Google and anti-virus vendors.

but I believe that refers to tools changing Chromium's policies, not to embedders like QtWebEngine using them.