D520 WiFi/bt5.0 card

If you want to trick out a system and find upgrades for it, you'd do well to learn its specs first by visiting support.dell.com and grabbing the User Guide.  You might also be interested in the Service Manual available there.  Anyhow, the short version is that the Intel 9560 specifically is out of the question, but you're also out of luck where Bluetooth 5 is concerned.  The Intel 9560 requires a CNVio interface, which is basically an interface that relies on the CPU having certain elements of the WiFi hardware built into it, and that's only found on the very latest Intel CPUs to have hit the market.  The 9260 is the equivalent model that has everything built into the WiFi card itself, but both of those cards use the M.2 slot standard.  The Latitude D520 uses the older Mini-PCIe standard.  The latest and greatest WiFi card that was made in that slot type before everything switched to M.2 was the Intel 7260, but it only supports Bluetooth 4.  The 7260 is also a half-height Mini-PCIe card, whereas the D520 has a full-height slot, so you'd probably need a half-height to full-height adapter bracket to install even that card in order to make sure you can fasten that card down into the chassis properly.  However, even then I'm not entirely sure you'll get Bluetooth specifically working, because I don't know if that slot includes the USB wiring required for Bluetooth.  On WiFi+Bluetooth combo cards, the WiFi portion interfaces over PCIe, and the Bluetooth portion interfaces over USB.  But on older laptops, Bluetooth was actually an entirely separate card from WiFi, and that's the setup the Latitude D520 uses, based on the fact that its Service Manual specifically shows that Bluetooth and WiFi are separate cards.  That said, it's possible that its Mini-PCIe slot nonetheless includes USB wiring, in which case Bluetooth on a combo card might work fine, with the possible exception that BIOS management and the radio toggle hotkeys may not work.  I would remove the dedicated Bluetooth module from the system if you try installing a combo card, though.

The somewhat good news is that the 7260 is only about $30, so it's not a particularly expensive experiment, and even if you don't get Bluetooth, you'll get much better WiFi out of the deal.  Just make sure you get the Wireless-AC 7260 rather than the Wireless-N 7260 (I have no idea why Intel used the same model number for two very different cards, but they did), and also get the 7260HMW rather than the 7260NGW, because the NGW variant uses the newer M.2 slot type, which your system can't use.  Good luck -- and grab that documentation from support.dell.com!