Yeah, they're probably not kyber powered beams, just laser beam weapons of the sort we've already seen at various scales from the LAAT side-gunner pods, to the Blade Wing prototype's main weapon, the SPHA heavy artillery, the cannon on the underside of the Venator, all the way up to the Death Star.
That said, the idea of a ship with a kyber powered weapons system, or even a specifically lightsaber powered ranged weapon is hardly without precedent. Not counting the Death Stars & Starkiller, the most obvious example is
this thing from the Temple's forbidden archives. Basically a lightsaber powered laser sniper rifle that can blow a hole clean through damn near anything.
Interestingly in the High Republic the Jedi Vectors require a lightsaber to unlock it's weapons systems. I'm not clear on whether this is purely a security/philosophical measure, or whether the kyber actually powers the weapons themselves. Probably the former, but the latter seems plausible enough, maybe in the distant past. Which takes us out of canon and into Lego of all things with the
Arrowhead, which is basically exactly that; a recreation of an ancient kyper-powered Jedi fighter design.
Honestly as silly as the Lego shows are (by design) the basic concept is sound. We already know that the ancient Sith (among others) made more than one kyber powered super-weapon, so why not something more in the mid-range? Personally I like the idea that the fall of the Old Republic and the rise of the various Sith Empires was essentially a galaxy wide apocalyptic event that brought with it the loss of an awful lot of knowledge and technology that's never been re-discovered.