I've been using LinkedIn with addy.io's aliases a couple years without issue, I can't say if that somehow makes your profile less promoted, I can only say that I've been receiving a few proposals here and there, don't have a lot of experience, so I think it's reasonable I don't get swamped in them.
To be fair though, the real privacy concern is all the information you have to share about yourself and that can't be avoided, regardless of the platform, you have to give details about you because that's the entire reason you would be on such a platform to begin with, to make yourself known.
What you can do is leave out all the details you're not comfortable sharing publicly and instead wait for recruiters to eventually ask you for those themselves, so you know that it only goes with one party that you have interacted with and can "trust", rather than the wider internet.

As for the email spam, there are a LOT of bs emails you receive by default from LinkedIn, but you can disable them, it took a while for me to figure out which is which because they have so many settings, but now I managed to have only what I care about, which is pretty much requests for connection and messages.
Also you don't have to install their mobile app even if they bug you about it, you can get by with the mobile PWA and if you want to do any Easy Apply job applications, you can just temporarily switch to desktop mode