The Offload Unused Apps feature on an iPhone is great to save space and keep devices secure. This keeps documents and settings for apps that haven’t been used for awhile but removes the app bundle itself. For those with a lot of “set it and forget it” sensors in the home it can be a bit problematic. Once an app is disabled, push notifications no longer get sent to the app. So if a carbon monoxide monitor or water sensor goes off, installed for a little peace of mind, then the app might not be alerting you (maybe an email as a backup). To disable this feature, open the Settings app, tap on General, then tap on iPhone Storage. Look for the section for Offload Unused Apps and tap the Disable button.
Another issue I’ve found is that some apps, when they update, clear the cookie/bearer token/oidc information/etc. Especially when developers are new to working with federated identities. Some store this information in volatile locations… So it’s a good idea to have a monthly reminder to open the apps and make sure they still work (like do they show that the water level is good, the CO2 levels are within boundaries, or whatever).