Governments (such as Saudi Arabia) often buy expensive hacking software from the companies abroad (such as NSO in Israel), needless to say with citizens tax money. Such software can hack into any phone, even with zero click. A mere phone number would be enough. They also have internal hacking teams and APTs, with own hacking tools.

Further, if you are in a country that manufactures key closed source components of the phone, you should assume that the government of that country can access the phone with the help of a backdoor or zero days embedded in the closed source software or hardware. iPhone is a good example.

Sandboxing in desktop is worse. Still you can better lock down a laptop if you know what you’re doing, since a computer is not linked to a phone number and you can leverage the flexibility.