[Bender]

Not so much switch, but rather "fall back to" a self hosted instance of uMurmur, IRC, etc... when Discord is down or if the topic is too sensitive for a shared corporate platform. People will stay were their friends are. Having a fall-back solution that gives them more privacy or a way to remain in contact when their primary means are down can be useful at times.

How vigilant people are about privacy will vary greatly by generation and by group interests.

[bogomil]

So in this case the trigger is the system is down and we need to understand how do we keep doing what we do as a group. But then when the main system is back, how do we keep them into the new one?

[Bender]

how do we keep them into the new one?

This goes back to the variation by generation and group interests. People that already feel oppressed by the main platform may likely stay on the one you provided them, otherwise most will go back to whatever they and their friends liked about their main platform. Unless these people are your employees it is unlikely you would be deciding where they go. Even in that case employees will do what they can do.

Ask these people what they like about the platform they are on and decide if you can replicate or enhance that experience. If you can, show them and they will decide if what you created is something they would prefer.