Yes, there is no issue in installing latest Distributions on the NitroPC, it comes with Tianocore, which is a UEFI enabled firmware. For displays, please check the product description in the shop (i.e., the display details), generally 4K works fine - it's better to use DisplayPort compared to HDMI. The shop gives an accurate indication, if some product is not in stock, so you can rely on that. As of today the NitroPC is in stock.