Beginning in Android 7, Google allows the Chrome APK to replace the WebView APK (they are built from the same codebase). If Chrome is installed, WebView will automatically be disabled. If Chrome is uninstalled, WebView will be re-enabled and can receive updates from Google Play. If you have developer options enabled, you can see which source your WebView implementation comes from.
From time to time I am contacted by someone who is having problems with Privacy Browser because they don’t have a functioning WebView on their system. Usually these are people with root access to their devices who have manually remove a bunch of Google software because they don’t like Google spying on them (a worthy endeavor). Typically they don’t realize the WebView is fully open source and a part of Android in a way that Google Play Service, Gmail, Google Photos, and other closed source Google apps are not.
To restore WebView you can use Yalp or Aurora to download the Android System WebView APK. Bromium also provides a fork of Android’s WebView called SystemWebView that might be worth trying. SystemWebView is open source, but I have not spent the time to inspect their code myself and users are advised to do their own research before deciding whether to trust them.