Take a look at my post on the Smartthings forum about a way to get Webcore and Node Red to work together - For a few months I was in the same place you are and ran both, before ultimately moving everything to Home Assistant. Hopefully this can get you through temporarily until you just get everything off Smartthings and moved over.
Also, try and look at the Samsung Automation studio node - which is another way to get Smartthings devices directly into Node Red. Haven’t used that myself but there may be more of an option to run automations with those nodes if devices are offline versus the Home Assistant Smartthings integration.
Ultimately I would just work to get off of Smartthings and get everything over to Home Assistant. I did that back in March and am relieved I don’t have to worry about the chaos going on over there anymore. Its a sinking ship and best to get out while you can. You will also be amazed at how much quicker everything runs with the local control.
Once your devices are on Home Assistant, it should be easy enough to setup notifications for when they go offline - see this post/thread Notify when a device goes offline - #7 by Burningstone