If you already carry a an iPad in your laptop bag, but use Windows or Linux on your laptop, you can use the iPad as an external monitor using: - a cheap HDMI USB capture device ($5 from Temu) - a short HDMI cable to connect that to your laptop's HDMI output - a USB to lightning or USB to type C adapter (depending on your iPad model) - a free app to display the UVC camera input full screen, e.g. https://apps.apple.com…
If you're using a mac you can extend your screen wirelessly to the iPad. I found the image gets compressed a bit but it's still plenty usable for showing a browser during web development.
Note: you refer to 'mac' (the hardware) but Sidecar is tied to MacOS (software). A Mac running Windows or Linux won't support Sidecar. A non-Mac running MacOS (aka hackintosh) probably will.
If you're running old Mac hardware like a MBP 2015, you can install Ventura (and user Sidecar) using OpenCore Legacy Patcher.