A solution is easy to implement and can be operated on a standby basis for just a few euros. The technology used is irrelevant: The spectrum of solutions ranges from a collaboration area in the intranet (if this is not also based on SharePoint Online) to an alternative collaboration tool such as Rocket Chat.
Many companies used Rocket Chat for a long time as an "on premises clone" to Slack & Co. However, due to the lightning spread of these cloud tools, Rocket Chat quickly lost its importance during the pandemic.
To get to grips with the issue of communication in times of crisis in a cost-effective manner, Rocket Chat represents a very simple option: In the app stores of the hyperscalers, prefabricated images can be booted up and used on an hourly basis. Ideally, a different hyperscaler should be selected than the one on which the standard collaboration solution is running. Safe is safe! Such a backup system for communications in the event of a disaster can be quickly configured and made operational by an IT department. Rocket Chat can also be deployed without permanent overhead via single sign-on and automatic software distribution capabilities.