Microsoft-owned LinkedIn is yet another social network that has decided it should not ask its users for permission, and simply opt them in by default and feed their data to generative artificial intelligence (AI) for training.
If you want to opt out of it, look for your profile image at the top of the LinkedIn menu bar and select Me. Under there, pick Settings and Privacy and then, the Data privacy menu item.

Look under "How LinkedIn uses your data" and pick "Data for Generative AI improvement":

It's set to "On" by default. If you don't want that, set it to "Off". How much LinkedIn will respect that is another matter, but at least you've signalled quite clearly you don't want "LinkedIn and its affiliates" to "use your personal data and content you create on LinkedIn" for GenAI model training.
Now, it's entirely possible that this could be something useful, but LinkedIn's FAQ on how it uses your data is opaque and doesn't spell out any particularly interesting benefits to those who remain opted in.
And, it's that last thing that should've happened first of all: a request to join the programme, after you've had a clear explanation as to what the data will be used for, including any privacy implications.
This might seem futile, given that LinkedIn user data has already leaked out in the past, but there's no requirement for you to offer up your new information willy-nilly.
A number of LinkedIn accounts won't be able to opt out by themselves, however. If you look at their profiles, you'll see why:

We live in the future.
Update Britain's Information Commissioner has told LinkedIn not to train AI models on users' content.
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