I’m in the UK and also fine on two phones and an ipad I have access to right now. Have you tried taking the app out of being optimised for battery life? Maybe the delay in it waking back up is causing it?
Very odd, but obviously, a service such as smartthings has many servers and points load balanced so it might not just be yourself but a subset of users. I would ping support an email to get someone to investigate.
FYI, I use BlockThis VPN (https://block-this.com/) which is free and works really, really well - blocks ads in webpages, apps etc and its never caused an issue for me.