And that’s a bad thing?
The desktop is finally catching up with the more restrictive permissions model where an app doesn’t just have the ability to do anything the user can do but instead only has access to what it needs.
Going with a familiar interface style like the ones people already use on mobile just makes sense.
What would you want it to look like instead?
While Signal does use Google’s notification system, my understanding is that they just use it as a way to wake up the app on the phone and have it check for new messages rather than sending any message content this way. The notification system that the operating system provides on the phone would still have access to the message data in the locally generated message notification with the actual content however, along with any apps that you give access to your notifications.
It may be something like Android System Intelligence or another similar service doing it: https://support.google.com/pixelphone/answer/12112173?hl=en
Notification management: Adds action buttons to notifications. For example, the action buttons could add directions to a place, help you track a package, or add a contact.
Supposedly Shreddit uses the archive of your data that you can request from Reddit to delete the stuff that isn’t currently viewable but I haven’t tried it first-hand (costs money). If you could feed the archive data into one of the other scripts mentioned in the comments here somehow, that would probably be the most thorough option, assuming you don’t hit an API rate limit.
Another KOReader recommendation here. I typically use it on an eink device but also have it on my phone and it works well.
Looks like for syncing there’s a plugin:
https://github.com/koreader/koreader/wiki/Progress-sync