[hailwren]

They wouldn't use the IMEI. Your phone also reports the IMSI which includes country code, network, and an identifier number. They'd only have to differentiate you from the other people from your country. By the problem statement, you didn't go straight to your hotel -- so you're probably going to be the only one.

And sure, you could leave it on airplane mode -- but you have to keep in mind that you are eventually going to be found, and I'm not really clear why we're even evading quarantine but when you are found the punishment is going to be much more severe if the government believes that you were intentionally avoiding detection. Keep in mind, Taiwan still punishes drug trafficking with death -- I can't imagine they'd look kindly on intentionally endangering their entire population.

Although upon further thought, IMEI should be fine too. Consider that international travel is mostly shut down right now. I'd be surprised if there are more than 500 international travelers at the airport within 30 minutes of you. They would just check every one against their quarantine reporting status (hint: EVERYONE else will be where they're supposed to be and checking in as part of the procedure) Then all you have to do is remove IMEIs that are at their correct reporting location one by one. I'd guess less than a hour's work given that the reporting is already being handled.