Technology

It's possible Signal could stop distributing the app through the Play Store and Apple App Store within Canada. Signal is likely to shut off all servers they rent that are hosted inside of Canada at the very least.

In terms of them deactivating people's accounts registered with Canadian numbers that seems less likely to me.

Even if they potentially blocked Canadian IP addresses, Signal already has support for proxies built in and those are ran by diverse people throughout the world. Some individuals host them.

This isn't exactly the same since each situation with each country is different in terms of the law but Signal is banned in some countries such as Iran, Qatar, UAE and others already and people still use Signal by using Signal TLS proxies, VPNs, and other censorship circumvention tools such as Tor.

They didn't deactivate accounts after being banned and they still allow phone number registration in those countries.

For Android people could download the apk file from Signal's website instead of getting it from the Play Store at least.

https://signal.org/android/apk/

While we don't know with certainty what they will do in each situation the past may be an indicator of what they will do to a large extent. But Signal has never pulled out of a country voluntarily before as far as I know so it is uncharted territory.

I think the intentional deactivation of current accounts is unlikely to happen in this case with Canada.