Bluesky appears to suffer from spam followers (new accounts which solely promote their domain(s)) — I gained several after following a handful of users, before posting or interacting with anything.
Bluesky sends a notification for each, grouped together with reply and quote notices.
Currently there's only one option in the notification settings:
Notification filters
Enable priority notifications ☐
⚠️ Experimental: When this preference is enabled, you'll only receive reply and quote notifications from users you follow. We'll continue to add more controls here over time.
You may post a userscript which automatically marks the follower notifications as read as an answer.