There's no hiding an AirTag from a thief competent enough to use Google. 30 seconds of googling and one app download, and you can find an AirTag to within a couple inches even without the speaker.

Once it's found, it's easily separated from the bike, and if it can be separated from the bike, there's no guarantee the tag hasn't been thrown into someone's backyard, thrown on top of someone's roof, dropped into a dumpster, taped onto someone's bumper, or slipped into an unsuspecting stranger's bag.

Further, the tag has no GPS of its own, so what's being reported are the locations of the phones that pinged it, not the location of the tag itself.

Yes, some people get lucky and airtags can help find particularly dumb thieves. But most of those dumb thieves are stopped by any lock that can stop bolt cutters, and almost all of those dumb thieves are stopped by angle grinder resistant locks, which you should absolutely be using for a $6k bike.

To be a effective GPS tracker, it needs to have its own GPS and its own cellular or satellite connectivity, so that it's not depending on other people's phones to ping it, and can't be easily found with a free app on someones phone. That means for all practical intents and purposes, it has to have a monthly or annual fee, since without it, it can't communicate effectively and in real time. Ideally, that tracker would be deeply integrated with the bike's electronics, so that the controller gets bricked if the tracker is removed while the bike is locked or in lost mode.

And as an aisde, GPS and cellular jammers do exist, but for the most part, they are too risky for bike thieves to use, especially on the go and for the time periods needed to steal bikes. GPS and cellular jammers are highly trackable, interfere with licensed frequencies of mobile carriers who are in turn highly motivated to track them, and tend to result in rather serious felony charges when done in conjunction with other crimes.

Security starts with locking up in a location that's well trafficked and highly visible. Don't try to hide your bikes, especially your expensive bikes, because you'll just be hiding the thief that's come to steal it. You want to be where there's people and cameras. Not because anyone will actually lift a finger to stop a thief, but because eyes always make criminals nervous.

Then you need a good, angle grinder resistant lock. That means Sold Secure Diamond, or ideally Powered Cycle Diamond ratings (sold secure is an independent rating scheme from the UK).

Any tracking you can add is better than nothing, but real 4G/GPS tracking is far better than bluetooth tags, and something fully integrated is better still.

And finally, if the best single lock you can buy doesn't come close to enough protection for the price of the bike, you need to insure it with a policy that actually covers theft, in case all else fails.