Note this answer is partially subjective.
As for the meaning, it is always appreciation of efforts. But it is used conventionally and the meaning is kind of worn out. So in some cases, it is just a way to say hi. In such cases it virtually means nothing. It is like dear... in English in the sense that you don't really mean dear in many cases.
When answering to the phone of friend/family
I don't think answering the phone from friend/family with お疲れ(様) is very common. If it happens, it is just carrying the workplace habit to the private life.
The 'hi' sense of お疲れ/お疲れ様です is used among colleagues (workers in the same company). For example, you write emails or talk on the phone/chat (slack, Teams or whatever), you start the conversation with お疲れ様です (お疲れ if you are in casual relationship with the addressee).
A similar phrase is (variants of) お世話になっております. This is used as an opening for a conversation with people outside of your own company (often customers). The usage does not really have anything to do with the meaning. You are usually expected to use it when addressing the customer for the first time.
I personally think this custom is rather weird, to say the least.