Anyone who's been trying to steal the whole town blind may have run into some issues when dealing with the art museum.

The doors are power locked and if you try to reach the control room at night there's a guard at the front door, along with a guard that patrols the stairs regularly. You can try to get in during the day with the contractors outfit and just wait it out till night, but this wastes a lot of time and also has the huge disadvantage of not letting you bring any tools to secure an escape.

Instead you can use the window right next to the scaffolding.

This window can be interacted with even if it doesn't seem like it. jump at the window a little ways back from it and you should briefly see the interact commands allowing you to use your crowbar.

once the window is busted open the window will let you climb through with a normal interaction.