How is the type of notification determined: Texts vs Apps

It is the notification actions that determines that. Which actions do you see in the notification on the phone? For the text type notifications you probably see reply and some more that are related to texts.

https://developer.android.com/develop/ui/views/notifications#Actions

Hi, interesting theory but unfortunately I don't think so the actions matter there. I just tested it with 3 different apps:

1. A notification coming from WhatsApp, being treated as "Apps" (not "Texts"). Available actions: "Dismiss", "Reply to <chat name>", "Mark as read", "Block App"

2. A notification from Google's Messages app, being treated as "Texts". Available actions: "Dismiss", "View conversation", "Block App", "Phone Assistant"

3. A notification from Signal, being treated as "Texts": "Dismiss", "Mark read", "Block App", "Phone Assistant"

Unless "Phone Assistant" notification action is needed for Garmin to treat a notification as "Texts" (instead of "Apps"), I don't think it matters..

Maybe I'm not understanding the issue here. In what way are they being or not being classified as texts? What is the difference in how they are displayed? 

On garmin watches (e.g. Fenix 8) you have separate settings for "Texts" notifications and "Apps" notifications. E.g. you can set "Apps" to not show at all on the watch while keep "Texts". Or you can set "Texts" to vibrate and/or make sound when received, while "Apps" to be totally silent.

And that's what I did. I want my "texts" to vibrate (so I'm aware of getting those) while notifications form "apps" to be totally silent. And yet notifications coming from some instant messenger apps like Messages, Telegram, Signal, Discord vibrate as expected (so they are treated as garmin's "Texts" category), while notificatoins from other instant messenger apps like WhatsApp do not (so they are treated as garmin's "Apps" category). I would like WhatsApp to be treated as "Texts" as well.

Ok. I thought it was the displaying of notifications, but they are working as they should with the option to reply to WhatsApp messages just like any other text app.

The SMS permission for the app tells if the app is able to handle SMS/texts so that could be used to select how the apps should be handled, but Discord or Signal don't have that permission. Signal had it a few years ago, but unless you haven't updated the app for a very long time you should not see that. WhatsApp got an SMS permission. Have you allowed that?

I gave SMS permissions to WhatsApp and it didn't help. I don't think Garmin Connect checks those permissions tbh (can it even access permissions of other apps? that would be a security breach kind of). I'm afraid it's somehow hardcoded in garmin software which apps are treated as "texts", though it would be weird to hardcode a niche app like Signal for that and not an extremely popular app like WhatsApp, so maybe there's some key differential here..

I landed here for the same mystery. I only want SMS ("text" in the English versions) to have a sound notification and vibrate, while all the others ("Applications") should only vibrate. The issue is that Microsoft Teams and a few others I use are considered SMS/text and also have sound and vibration. This behavior forced me to disable the sound notification for SMS, which is bad.