If you refer to the Apple KB here, or to what other users seem to experience on the web (maybe because they have only 2 keyboards set up...), you would expect that the Switch Keyboard key 🌐 would do a circular shift of one increment in your list of set up keyboards in Settings each time you tap it.
For me it does not. Instead, the switching order seems rather random (I have 7 keyboards enabled). I can't get to understand the behavior or to find a pattern.
Has anybody the same issue? I am asking because daily I use only 2 or 3 of them, and it is "annoying" to open the full list by holding the button when typing.