Cheap HDMI capture for Linux
You can also use devices that are USB Video Class (UVC) compliant, thus which don't require any drivers.libuvc can be used to capture from these devices:
https://github.com/ktossell/libuvcYou can get cheap off-brand UVC USB grabbers, or you can get higher quality gear, like the AJA U-TAP:https://www.aja.com/en/products/u-tapAdmittedly though I haven't seen anything that comes close to £45 :-)