We have a baked thing here that looks like challah and must be very similar to it regarding the ingredients too… Not like it matters when it comes to my answer.
Yep, there is raised keto bread and all other raised bread relatives (but looking at google, maybe they are still considered bread). It’s easier with challah as it’s not almost just flour and water…
It is raised so we need gluten but gluten is pretty low-carb. Many people has problems with it though. I don’t. So I use gluten and some oily seeds, often a tiny bit of bamboo fiber, phyllium husk… But despite it noticeably raises and becomes fluffier as a dough, it is too dense when I bake it so if I want a somewhat fluffier texture, I can’t avoid using starches. It changes the taste too. I find gluten slightly bad tasting so I can’t depend on it too much and anyway, it’s so very flexible, it would mess with the texture. Pure fiber has no taste (well I have apple fiber and it has a subtle apple flavor…) and mess with the texture, at least in some cases. So I don’t depend too heavily on any flour replacement (probably almond flour is the best regarding this but I am not willing to buy that horribly expensive and not even particularly great tasting - just neutral, it’s precious but not for that price, for me - ingredient) but mix them.
If a baked good has eggs, that makes things easier as eggs are tasty and I am into them especially if I make bread. Eggy breads are the best if you ask me. So I just use more eggs than the recipe says and skip some liquid or add more very absorbent flour replacement (there is a limit as they are too tasteless but if it is a tasty, sweet dough, I can get away with some coconut flour… a tiny bit is possible for savory ones if I use sesame, that’s bitter and the sweet coconut balances it out without making the result too sweet). The tasty yolks mask the not so stellar flavors… If the bread can’t handle so much yolk but it has some liquid I can reduce, I just use more whites. Almost tasteless, has a lot of water but protein too, what not to like?
I personally use as much walnut as I can get away with as it’s very tasty unlike many of my options. For example, flax, even the nicer golden one (better for the color too but if I make a really low-carb bread, it won’t be white. not like my wheat bread would be light so it’s fine in this household) isn’t that tasty if I use much… I baked a lot in my paleo-ish low-carb years and had to mix my “flours” to get some okay result. It never was good for raised bread but it was edible. I personally just make some hybrid bread nowadays, it’s enjoyable (better than the carby one, better than the keto one, fluffy enough texture, good taste) and I don’t often eat such things and can handle that much.
So, according my own tastes, if I just want a braid a sweet, raised bread, I can do it keto but it won’t be as pretty and especially not as enjoyable as a somewhat starchier version. But if the goal isn’t making a tasty, fluffy one, a keto version seems quite possible. (I know I can make a similar keto stuff but maybe there are conditions for challah I don’t know about, who knows?)