Just mail it as a gift, portable game console or whatever, why would it be a problem ? With the factory firmware it should meet local requirements , but i have ordered other hardware described as a wireless receiver, that had a bunch of antenna’s for other purposes but it never caused a problem. It’s not like they are actually gonna try to read documentation about random products sent trough customs.
If you order “signal generators” on known Asian platforms, those devices , for testing purpose are not illicit by themselves, but they have potential illicit uses, back 10 years ago nobody cared, but even nowadays, if you do not put “shady hardware” on the label its not like they will actually function-test devices on border checks. So as long as you do not plan to sent out or receive controlled substances i think you will be fine.