The recently launched iOS 15.4 update comes with a rather useful feature. It lets you unlock the phone with its Face ID when wearing a mask. According to Apple, it scans the "unique features around the eye area." But it looks like the feature requires more resources, as the company seems to be limiting its availability to newer iPhone and iPad models.
According to 9to5Mac, the feature is limited to these iPhone models:
As for iPad models, it looks like the 2018 iPad Pro models don't support the feature.
If you have an iPhone X, XS, or 11, the alternative is to unlock your iPhone with the Apple Watch.