Yes, they have PCIe slots. What you need to concern yourself with is the power requirements. What kind of power supplies are in these computers? Do they have enough connectors for the GPUs. (If they don't, it is a strong indication they aren't big enough) You'll be wanting something in the 500W range for the 2070/2080 and 600W for the 2080Ti.
Obviously pairing such large GPUs with things like celerons and pentiums won't do so well. i5 and up preferably.