The article is specifically not referring to information that's sent to Apple servers - it's about information on the phone only, accessible through forensics tools with physical device access.
Signal's server-side push notifications only contain a "wakeup" message. The actual message popup is displayed after decrypting the message contents locally on the device. Of the things you mentioned, only the time of notification is visible to Apple/Google.
Fun fact, apps can't wake from APNS if the user killed the app (swipe up) last time instead of switching away normally. Apple publicly said something contrary to this at one point, so it might be surprising that Signal can work this way. The notification itself will still come through outside the app, so I wonder what you see, probably some placeholder text?
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The article is specifically not referring to information that's sent to Apple servers - it's about information on the phone only, accessible through forensics tools with physical device access.
Signal's server-side push notifications only contain a "wakeup" message. The actual message popup is displayed after decrypting the message contents locally on the device. Of the things you mentioned, only the time of notification is visible to Apple/Google.
Fun fact, apps can't wake from APNS if the user killed the app (swipe up) last time instead of switching away normally. Apple publicly said something contrary to this at one point, so it might be surprising that Signal can work this way. The notification itself will still come through outside the app, so I wonder what you see, probably some placeholder text?
Yes there's a placeholder in that scenario Something like 'new message available' if I remember correctly (I'm no longer on iPhone, so can't verify)