Desktop Safari to iOS native app Handoff opens iOS Safari

Question

I try to implement Web-to-Native handoff for my iOS app. I uploaded my apple-app-site-association file and it seems OK:

{
    "applinks": {
        "apps": [],
        "details": [
            {
                "appID": "XXXXXX.com.myapp",
                "paths": [ "/*" ]
            }
        ]
    },
    "webcredentials": {
       "apps": [ "XXXXXX.com.myapp" ]
    },
    "activitycontinuation": {
        "apps": [ "XXXXXX.com.myapp" ]
    }
}

Universal links and web credentials both work just fine, but Handoff doesn't. When I open my URL in Safari on macOS, my iOS device shows handoff for Safari, not for my app. I double-checked my code, I do have all entries in entitlements, like

activitycontinuation:alpha.mysite.com

I also tried

activitycontinuation:*.mysite.com
activitycontinuation:mysite.com

I implemented -application:continueUserActivity:restorationHandler: method, and even added these lines in my plist:

<key>NSUserActivityTypes</key>
<array>
    <string>NSUserActivityTypeBrowsingWeb</string>
</array> 

But iOS still shows Safari in handoff, not my app.

This is what I found in device console log:

Dec  8 19:30:04 iPad-Valentine-2 swcd(CoreUtils)[255] <Notice>: Trying add of app ID 'XXXXXX.com.myapp' for get info
Dec  8 19:30:04 iPad-Valentine-2 swcd(CoreUtils)[255] <Notice>: ### Add service '<<NULL>>', app ID 'XXXXXX.com.myapp', domain '<<NULL>>' failed: -6727/0xFFFFE5B9 kNotFoundErr

But I can't find out what does that mean.