Yeah, but unfortunately it is impossible to buy a phone without that

So i support Google by using an open source OS? Just because your phone uses Android dosent mean it has any Google services included. Since Android itself is open source, there are many Android OSs that dont include any Google Software.

but also need to comply to governments.

I dont know about every country, but as far i know in germany at least you only need to disclose the information you actually have. Eg: if you dont have the encryption keys, the government cant do shit with the encrypted messages they habe

So, correct me if im not right, but a messenger could be privacy respecting and legal at the same time

If Meta would really not know your Messages and encryption Keys, they would not be able to recover Every single one oft your messages even if you forgot your Password.