You're absolutely correct. Living in the core of the empire or within one of its beneficiaries affords certain advantages which are made inaccessible to those outside of those regions. Your best approach is likely assuming your mobile device is compromised and only conducting sensitive activity on an inexpensive laptop you can reasonably secure.

Some secure-by-default Linux OSes I'd recommend are:

Parrot Security OS https://parrotsec.org/

Tails OS https://tails.net/

Qube OS https://www.qubes-os.org/

These are listed from most user-friendly to least. Signal has a desktop client that I'd be comfortable using on any of those three platforms.