First off i want to say that no, there is no official sli support, but it is easy to get working, although it will only work with dx11, and not dx12.
1. First off you need to download the program Nvidiaprofileinspector version 18.104.22.168 , and run it.
2. Then you need to choose the "battlefield v" profile.
3. Set "SLI compatibility bits dx10 + dx11" to : 0x080116F5
4. Set "Nvidia predefined number of GPUs to use on SLI rendering mode DX10" to : 0x00000004
5. Set "Nvidia predefined SLI mode on DirectX 10" to : 0x00000002
6. Set "Anisotropic filtering mode" to : user defined (these filtering changes will prevent texture issues while using sli)
7. Set "Anisotropic filtering setting" to : x16
8. Set "Texture filtering - Quality" to : High quality
9. Set "Texture filtering - Negative LOD bias" to : Clamp
10. Set "Anisotropic filtering HQ Fix" to : On
11. Click Apply Changes and close nvidiaProfileInspector
12. Go to "C:\ProgramData\NVIDIA Corporation\Drs" and select both nvdrsdb0.bin and nvdrsdb1.bin and set them to read only.
Sli should now work with dx11.
Additionally sli works by far the best with motion blur set to 0 and future frame rendering set to ON in the ingame settings.
Issues using this profile is that dynamic wether effects (such as snow and rain) doesn't render. However, the profile provides about 97% sli scaling, provided nothing in your setup is bottlenecking it.
UPDATE : It appears that the ghosting introduced by sli has been fixed !
The sli profile running on my rig at 4k ultra :