It depends on what your threat model is. If its individuals, local law enforcement, or even national law enforcement (context dependent) you are trying to hide from, you can obtain phones with cash and make it very difficult to link them to you (use a sim card bought with cash and never give out that number, use a VOIP service for your primary number, use an OS that doesn't send back much telemetry, turn off location, never use the phone near your home, etc).
If your threat model includes targeted attack by a major intelligence agency, just accept that you are likely screwed.
If your threat model includes targeted attack by a major intelligence agency, just accept that you are likely screwed.