Re: So tomorrow Signal, Telegram?
> If I sell a rebranded chinese phone tomorrow with Signal on it, does that make me a criminal?
If you sold it to a drug dealer who uses it to evade detection while committing a crime - i.e. dealing drugs - then yes, you are an accomplice.
At a minimum, by selling this phone, you profited from the illicit gains of a criminal enterprise. The drug dealer paid for this phone with his drug money. It will be very hard to prove that the phone was paid for by the drug dealer with money obtained from a legitimate enterprise.
If you gave it away for free to the drug dealer, you aided a criminal in evading detection during the commission of a crime, because you installed Signal on it. Installing Signal has knowledge value - you know that Signal has strong encryption, which is why you installed it in the first place - and labor value - the manual effort of installing Signal. That also makes you an accomplice.
Best course of action: don't sell, or donate, mobile phones to drug dealers.