It is a cat-and-mouse game. In the UK, when email rules started getting enforced, politicians moved to WhatsApp and then Signal. If Signal becomes subject to enforcement, they will probably find other ways; and the collateral damage will likely be that everyone's messages will become fair game even more than it already is.

The reality is that backchannels have always existed. People used to meet discreetly or through emissaries; or had phone calls from secure lines; etc. There is so much that we will never know, even about times that are well-documented.

To be honest, I am not a big fan of "thoughtcrime" being pursued. Let them be racist if they want to; we should make sure the population is smart enough to reject racism on its own. Maintaining a working democracy requires some violence, sure, but if we over-use it it will stop being a democracy.