The menus used to be available on My Viking Journey (after you book), but since the pandemic I haven't seen any way to know the menu until you board. (I suspect the change was made because of worries about pandemic supply change issues, but kept it because there wasn't a large push-back.)
They seem to start a new three day stretch of a menu at the start of a cruise, but there probably isn't a consistent first menu.
We are happy reserving Chef's Table without knowing the menu, and would encourage someone who likes that type of meal to do that. The restaurant will create substitutes for anything on the menu if you ask. I'm a vegetarian so I sometimes have three substitutions in the five courses. My wife has nothing she can't eat, but about half the time she has a substitution as she prefers not to eat duck or lamb.
We make as many reservations as we can before the cruise, and on the first day try make more to hit other menus -- with no care about what is actually on the menu.