This was annoying me also so I looked into it and found a solution for android.
One way of addressing this is to filter notifications by text and ignore those that you are not interested in.
Native Android only allows full system and per app notification customisation, it does not allow for per notification within an app.
However one app that allows notification text filtering is Macrodroid.
By installing Macrodroid and creating a Macro trigger for a notification from the Smartthings app with specific text e.g. hub offline and then performing an action such as stop sound or enabling Do Not Disturb and optionally adding time constraints you can customise how your device behaves upon receiving particular notifications.
Rather than creating a blacklist of notifications to ignore which could grow long and would allow notifications through where the text is changed on the Smartthings platform or new alerts are introduced, it is easier to create and manage a whitelist of notifications that are allowed.
I wanted additional flexibility that allowed me to disable all notifications even those whitelisted if I chose (you can disable macros but I wanted to manage it via the native do not disturb). I also still wanted the notifications e.g. informing of app updates etc, just not the sound or vibration at specific times.
Therefore I set the macro Action to create a new Notification and in Android’s Do Not Disturb settings I configured Macrodroid to enabled/priority and all other apps including Smartthings to disabled.
End result is I still receive all Notifications from Smartthings but Android’s Do Not Disturb means no disturbance at night. However Macrodroid filters on notifications from Smart Home Monitor e.g, Front Door Intrusion detected and creates a new Notification which Do Not Disturb allows to trigger at all times (you can choose the sound in the macro).
I no longer receive annoying alerts in the middle of the night saying hub disconnected, app update available, hoover offline etc - I can review the silent notifications received overnight the next morning.