Any WebView is OK!
It tries to detect all system webviews and add them to the developer options -> WebView implementation list.
Android Framework should be selected in LSPosed.
A webview app must be installed for all users (or in all spaces, so-called Dual app, Second space, etc.) to be selectable. Maybe deleting redundant users is alternative. adb command:
Enable "redundant packages" (Maybe it won't work, but that's OK.):
adb shell cmd webviewupdate enable-redundant-packages
Get USER_ID list:
adb shell pm list users
Each user entry is as follow: UserInfo{USER_ID:USERNAME:INT} , USER_ID 0 is the main user.
Install apk for specific USER_ID:
adb install --user USER_ID PATH/TO/APK/ON/COMPUTER
or
adb shell pm install-existing --user USER_ID PACKAGE.NAME.OF.APK (for apks already installed for one user)
or
adb push PATH/TO/APK/ON/COMPUTER PATH/TO/APK/ON/PHONE (copy an apk file to phone from computer)
adb shell pm install --user USER_ID PATH/TO/APK/ON/PHONE
Delete a user (NOT RECOMENDED, be careful, you may lose important data):
adb shell pm remove-user USER_ID
All the adb shell pm ... commands above can be run in an Android terminal simulator(root access granted) as pm ...
Reboot to take effect.
Can I set Chrome as the system webview implementation?
Only supported on Android 8-9, not supported on Android 10+. It is Google's policy that Google Chrome app is no longer the WebView provider in Android 10. Even though it is listed in the WebView implementation, it does not work on Android 10+. Related discussion: AnyWebView#12
Is Bromite/Mulch/Vanadium etc. system webview supported?
Yes.