How long has it been there? It looks like it's been painted over at least once, so it might have been there for some time. It does seem to have a little displacement in the plane of the wall, so yes I guess you could call it structural. I'd measure the width and projection and monitor to see if it changes seasonally or long term.

it’s been there for quite a while. i had an inspector (not a strcutual engineer) come in and said that the displacement is likely due to thermal expansion.

He said it's a typical crack that is common in old homes and just monitor it. No action needed unless it leaks...

If the crack follows the mortar joints and doesn’t expand, I wouldn’t worry about it yet. If the crack goes through a block, it’s a structural concern and should be monitored closely.

it goes through a clock that's why i doubt the inspector's opinion