unable to input 0x1XXXX characters from unicode keysyms (linux, gnome, wayland)

first off, this is a very niche corner case. i have been trying to make keyboard layouts for ancient languages directly mapping the keys to unicode characters, e.g. character 0x103A0 (old persian "a") to the letter a as 0x010103a0, as for some reason extended unicode keysyms need to be offset by 0x01000000.

the issue

using whichever QT5 app including a demo i wrote myself, the keyboard doesn't input any character. pasting the characters from somewhere else renders correctly.

using a demo QT6 app it works fine.

to be clear: the layout works as expected everywhere else, libreoffice, gnome apps, firefox etc.