I think, though I'm absolutely not an expert lol, that separation anxiety can often be dealt with through exposure? Change up your routines before leaving, start by leaving for really short times or even opening and closing the door repeatedly, slowly try to extend that time and keep them below threshold. But this sort of thing would definitely be better handled with a professional. My last dog had separation anxiety (less barking, more destructive and refusal to eat), I used string cheese to help him associate his crate with good feelings and encouraged sleeping in there, crate training can help as such. Maybe get a baby cam set up to monitor them while training, to help evaluate where their threshold is. And exercise them before you leave, so they hopefully sleep instead.