Are you able to update it from this link? They have an annoying habit of dropping support for older versions of Android so you may be SOL.
Are you running a custom ROM? The webviews you can install on stock ROMs are restricted to specific publishers (usually Google and the phone vendor), but LineageOS adds a few extra accepted certificates for FOSS webviews and some ROMs disable the webview signature verification entirely. You may be able to find a modern version that's installable on Android 9 with some searching.
Edit: the Bromite project is sadly long-dead, but they have an excellent writeup of how it all works here.