I noticed something just now: if you try to search for example
translate !kf
it opens kagifeedback at
https://kagifeedback.org/?q=translate
but if you search translate on kagifeedback the actual url is
https://kagifeedback.org/?q=translate%20
and yeah... somehow the last url there works but the !kf url doesn't work. i'm not sure what that space (%20) at the end is being added for, but it seems to work.
you could change the bang but this feels like a Flarum specific issue that needs to be fixed