[smoldesu]

Many recent machines (including Framework iirc) have socketed wireless chips. If you wanted, you could pop out the internet module and be forced to use it offline until you bother yourself to get a screwdriver and reboot your machine.

If a new laptop isn't in your budget range, there are a lot of used machines with hardware-based wireless modules that you can disable. Shop around, you'll certainly find something that fits the bill.