I don't have a gravel bike but I've done a bit of mountain biking in extremely dusty conditions. If I use a light chain lube it seems to get pretty dry after a couple hours in the dust, but when I use Finish Line wet lube, it stays lubed a lot longer. Sure, it's messy, but it stays on.
To be honest I am terrible at maintenance and definitely don't obsess over drivetrains. If I did have a gravel bike it would get the same lack of attention as the rest of my bikes.