Unless I've missed something big, they cannot "scan" Signal messages. This would require a backdoor into Signal. This would be bigger news than the Online Safety Act.
Discussion
Signal will likely have to abandon that market
So far, they aren't backing down (afaik), and good on 'em.
I don't wish it on anyone, but maybe if a nation becomes enough of a digital backwater, they'll push back en masse.
I don’t use Signal but I suspect you are right. Access to Signal will end in due course. We shall see.