Watching the news this morning, apple security issues past boyfriend tagged his ex. This is for personal security how to remove unwanted tags.Without an iPhone you are just going to have to find it like you would any transmitter. The AirTag is a Bluetooth device, and it can be seen by a Bluetooth browser on a smartphone or tablet. You can use the RSSI to track it down, but it will be tedious.
If you do have an iPhone and you get an alert about an AirTag moving with you, you have the option to locate and/or disable it. This Apple video has some information. So it depends on what you have and why you think there is an AirTag nearby.