Sent this to my manager, who is a scot on the east coast of Scotland. I can understand him just fine, unless he starts using Scottish colloquialisms.
I spent a week in Glasgow for work back in 2019 and have a distinct memory of walking down the street and seeing a guy walking towards me while talking on the phone. I knew he was speaking English (rather than some foreign language) but I'll be damned if I could understand anything he was saying.
Chris