There are ways the government can force the ISPs to shutdown the internet, like cutting their electricity or takeover their system... Even if solutions like Bridgefy works, they still cannot communicate with people outside the nation, and I wonder if the government can just find out people using the system and arrest them.
I think it would be more useful to think of measure to hide under surveillance, and access outside information even if ISP block some of the connections to outer internet. This is what currently happening in China, an arm race between the state and developers.