On GrapheneOS, webview is Vanadium browser based. No invasive Google spyware.
Keychat uses the OS WebView for it's browser. The Android OS webview is Chromium based.
https://github.com/keychat-io/keychat-app/blob/main/packages/app/lib/page/browser/WebviewTab.dart
Discussion
Unlike on desktop, where the Nostr ID is a browser extension, in Keychat, the browser (WebView) is an extension of the ID and BTC wallet.
Vanadium is Chromium based but with a lot of security and privacy changes. Because Vanadium is also the OS WebView you can run apps using WebView in a safer fashion, they benefit from such features:
https://grapheneos.org/features#vanadium
Also a control for WebView JIT per app to reduce a large JS JIT attack surface for them. Our PDF viewer is an example of a WebView app.