I'm not who you responded to, but the DeckLink Mini Recorder (towards the bottom of https://www.blackmagicdesign.com/products/decklink/models) is a very capable PCI-e HDMI and SDI capture card for around £100/$140.

Apart from possibly needing an update to the kernel package, all of the DeckLink devices are supported by the same SDK, with only some small variations (like giving the user the choice of selecting which input connector to use or similar).