Generally speaking, if a breaking change is bound to the chosen technical stack that powers your Functions App, I believe your Azure sub is auto-detected by us and you will then be getting notification emails ahead of time. You'll also want to leverage the open-source nature of Azure Functions and get subscribed to the multiple announcement sources below:
- Azure Updates, an example from Node 10 deprecation: https://azure.microsoft.com/en-us/updates/azure-functions-support-for-node-10-is-ending-on-30-september-2022/
- Functions Announcements: https://github.com/Azure/app-service-announcements/issues
- Azure App Service Team Blog: https://azure.github.io/AppService/
Assuming that you are getting notifications from Azure as well as subscribed to the announcements sources that are publicly available above, Azure Functions as a PAAS guarantees 99.95% uptime (SLA for Azure Functions) for running your functions in their intended functionality.