Vivaldi is using the messaging hosts declared in registry directory of Google Chrome. Therefore selecting Vivaldi in the settings of KeePassXC will fail to enable the plugin.

Expected Behavior

Activating browser integration for Vivaldi in the settings of KeePassXC sets the NativeMessagingHost for Vivaldi and the extension can connect to the browser.

Current Behavior

The NativeMessagingHost ist set in a directory of the registry that is never queried, therefore no NativeMessagingHost is registered. The extension does say so when being debugged.

Possible Solution

Just do the same for Vivaldi on Windows as you are doing when activating browser support for Google Chrome, e.g. create the NativeMessagingHost not in "\HKCU\Software\Vivaldi\NativeMessagingHosts\org.keepassxc.keepassxc_browser" but in "\HKCU\Software\Google\Chrome\NativeMessagingHosts\org.keepassxc.keepassxc_browser"

Steps to Reproduce (for bugs)

1. Use Windows
2. Enable Browser integration for Vivaldi
3. Install extension in vivaldi
4. Try to connect to database (fails with silent error ->debugging says no native host found)

Debug info

General Info

KeePassXC fork - 2.3.0
keepassxc-browser - 1.0.1

Operating system: Win10
Browser: Vivaldi
Proxy used: YES (but obviously the same with no proxy)