How do you handle self hosted tools when the internet goes down completely?

I have been thinking about self hosted tools that still depend on the internet for setup, updates, authentication, or sync, and it made me wonder what true offline use looks like in practice for people here, so what does offline first actually mean in your self hosted stack? Most of us deal with power outages, ISP failures, travel, or remote locations where the internet is not available, and a service that breaks without a connection is not really self hosted in that moment Do you keep local mirrors of package repos, how do you handle authentication when the identity provider is offline, and what do you do about mobile clients that expect cloud sync? This is useful to discuss because offline resilience changes architecture, backup strategy, device choice, and even which apps are worth using, and many people only discover the gaps when they are already offline I would love to hear concrete examples, failures, and lessons from your own setups, especially anything that works without any internet at all, so what is the one offline tool or service you trust most when everything else is down?