TikTok did the same shit back when I used it. It's weird because I've always kept my internet life separate from my personal life, and now every app is begging to show my closest friends and family my shitposts, political takes and NSFW content. I'm mostly done with traditional social media by now at this point anyway. I've managed to kick tiktok and am now permanently banned from reddit so hopefully I won't get sucked back in.

I'm pretty sure they connect it to your device ID

I redownloaded Snapchat today on my degoogled phone since my friends use it all the time now and I've also seen that it somehow got all of my contacts. Turns out that it uploaded my contacts to their cloud without me clearly telling that when I first signed up.

To check if your contacts are in cloud: Go to your profile > Open "Settings" by tapping the cogwheel > Under "Account Actions", select "Contact syncing" > Tap "See contacts shared with Snapchat". You can delete your contacts there too, I just did that. If you have an Android phone, I'd recommend you to patch your app with something like ReVanced to minimize data collection.

I've disabled it on the system level and on my Samsung phone it doesn't send those notifications. idk if calyxos will have the ability to do that once it comes back.