I’ve researched this for probably the same reason. The simple answer is „no“. As far as I know you can locate an AirTag through the Find My-App on a Mac, but you can’t add one to your account.

Retrieval of the data from Apple requires an iCloud account and the keys required to decrypt it is stored in the key storage of your iDevices.

By my knowledge it seems to be theoretically possible to use the network with no iDevice and a bunch of faking, but I think it hasn’t been done so far.

For work around the network you may be interested in OpenHaystack (custom trackers and client, https://github.com/seemoo-lab/openhaystack) and Send My (custom messages over the network utilizing OpenHaystack, https://github.com/positive-security/send-my).

It’s not possible, although they can be reprogrammed so perhaps in the future someone will write a custom firmware.