Facebook video covers with DaVinci Resolve
Setting up DaVinci Resolve for making a Facebook cover video is quite simple. The only things you will need to set up is resolution, clip length, and the file shouldn't exceed 1.75 gigs.
A minimum of 20 seconds long but can't exceed 90 seconds long.
To change the resolution click the gear in the lower right. Within the project settings click on master settings.
For facebook I just use MP4(h.264)