One solution is likely the same as the one that stops every other iOS update from re-enabling iCloud password sync: Create a profile using Apple configurator <https://apps.apple.com/de/app/id1037126344> that forbids all these AI features and upload it to your devices.

The other solution is to say goodbye to these products that don't respect you.

By the way, if you're annoyed by the new huge "sync" menu entry on Firefox, you can disable it under about:config by setting identity.fxaccounts.enabled to false. Again, a lack of respect, this time by Firefox, for forcing this stuff down our throats. I'm only using Firefox because the alternatives are worse in terms of privacy. Ladybird, we're waiting for you!