The answer is mTLS.

But you will run into the key distribution problem. But if your number of devices is manageable, it could be the solution

Then follow that path, once you are comfortable with the approach you can start hosting more and more services,to the point that you can selfhost your own messenger services or ms teams services.

Once you are in that situation, you can think in accounts rotation and/or burner identities to address the services you can not pull from the big techs

You need to start reducing your fingerprint on internet.

The only reliable way to do so is selfhosting your stuff.

There are a few communities here in lemmy, so check on them