Reproduced using com.android.tools.build:gradle:4.0.0-alpha08, only if android.enableR8.fullMode=true
Full source code available: https://github.com/shadowsocks/shadowsocks-android/commit/ef1bd7d70d1fc4427425e8d5a27470f437a88742

Using `-printconfiguration` in Proguard rules I can see that this is present as expected, even in full mode:

-keepclassmembers,allowobfuscation class * extends androidx.lifecycle.ViewModel {
<init>();
}

When running compiled release version, it crashes with `Cannot create an instance of class com.github.shadowsocks.net.HttpsTest`, which extends ViewModel.

Output of -whyareyoukeeping class com.github.shadowsocks.net.HttpsTest { <init>(); }:

com.github.shadowsocks.net.HttpsTest
|- is referenced from:
| void com.github.shadowsocks.widget.StatsBar.testConnection()
|- is invoked from:
| boolean com.github.shadowsocks.MainActivity.onKeyShortcut(int,android.view.KeyEvent)
|- is defined in library method overridden by:
| com.github.shadowsocks.MainActivity
|- is referenced in keep rule:
| ./mobile/build/intermediates/aapt_proguard_file/release/aapt_rules.txt:18:1
Nothing is keeping void com.github.shadowsocks.net.HttpsTest.<init>()

Related but closed issue: https://issuetracker.google.com/issues/144514795