Branch protection setting 'strict' conflicts with Mergify configuration

We use Dependabot and Mergify in the same repository.

Dependabot will automatically keep PRs up-to-date with master, unless some other actor has meddled with the PR in the mean time. So if Mergify tries to merge from master, Dependabot stops keeping the PR up to date.

Dependabot can do a better job of keeping the PR up to date, since it can deal with conflicts in package-lock.json etc, so we'd like to keep this job for Dependabot and disable Mergify's "keeping the PR up-to-date behavior."

Unfortunately, just setting strict: false won't work, because Mergify will complain with the above error message:

Branch protection setting 'strict' conflicts with Mergify configuration

Which is correct: our GitHub branch protection setting is strict, but we want Mergify to accept that and merge the branch whenever all branch protection settings are satisfied, without trying to keep the branch up-to-date itself.

If we're going about this the wrong way, I'd like to hear the recommended configuration of Mergify in conjunction with Dependabot.

(*) It is not an option for us to rely on Dependabot's own merge behavior as that requires a company-wide switch that any org member can toggle, which we cannot rely on in an org of ~1000s of people.

No files or tests are named. Start by reviewing Mergify's branch-protection and update behavior alongside GitHub's strict setting and Dependabot's updates; done means a documented or implemented configuration that lets Dependabot keep pull requests current while Mergify merges once all branch protections pass.