One odd distinction is between social networks where the notifications are really notifications about people engaging with you (Mastodon, Bluesky, Facebook, Instagram. Tumblr) and ones where it is mainly spammy events that they blend in so you get a double-dose of spammy algorithmic feed items (LinkedIn, Threads)

One think that has me LFAO about LinkedIn is that normal social networks chime you when somebody responds to your content, LinkedIn chimes you when you post something, just to reinforce that it's a step lower on the food chain.