Depending on where you're based, you'll find PayPal's new data-sharing option under a different name. Remember, you may not see this at all if you're based in a country that doesn't allow it.
If you're in the US, you should head to your profile Settings and tap on Data & privacy. Under Manage shared info, click on Personalized shopping. You should see the option enabled by default. Toggle off the button at the right to opt-out.
If you are in the UK like me, you'll see something different after you head to your profile Settings and tap on Data & privacy.
Under Manage your privacy settings, here you'll see an Interest-based marketing tab – click on it. At this point, two options will appear: Interest-based marketing on PayPal and Internet-based marketing on your accounts. You have to tap on each of these and toggle off the button at the right to opt-out. These instructions can also apply if you're based in the EU.
In the EU this kind of automatic opting-in to marketing/data sharing is against the GDPR as it requires explicit consent from user/customer. I'm in the EU and have those settings but they were both toggled off, as expected.
Spain here, and both were turned on by default. Had to deactivate.
Same in Germany
Just checked it on three different accounts (germany) and each one had those two options turned on.
Mine was already opted-out.