Libra 2 Struggling to change system UI (Avenir) font to another one with Cyrillic support

Hi
I've tried to change the default system GUI font Avenir (header, footer, series names in My Books tab) to another one with proper Cyrillic support without success. The main reason is that the Ukrainian text looks weird, while the English one looks normal.
I've tried it with both KoboPatch (files section) and by replacing fonts manually in KoboRoot.tgz, like described here:
https://www.mobileread.com/forums/sh...54&postcount=7
AFAIK, the font names should be changed in font metadata to match the default Avenir ones. Also tested with upgraded Avenir from this post:
https://www.mobileread.com/forums/sh...36&postcount=1
Then, I've found the next thread, also without success:
https://www.mobileread.com/forums/sh....php?p=4331303
I also tried it with the Ubuntu font family.

Here is my snippet from kobopatch.yaml:
files:
src/adds/fonts/Avenir.ttf: usr/local/Trolltech/QtEmbedded-4.6.2-arm/lib/fonts/Avenir.ttf
src/adds/fonts/Avenir-Bold.ttf: usr/local/Trolltech/QtEmbedded-4.6.2-arm/lib/fonts/Avenir-Bold.ttf
src/adds/fonts/Avenir-BoldItalic.ttf: usr/local/Trolltech/QtEmbedded-4.6.2-arm/lib/fonts/Avenir-BoldItalic.ttf
src/adds/fonts/Avenir-Italic.ttf: usr/local/Trolltech/QtEmbedded-4.6.2-arm/lib/fonts/Avenir-Italic.ttf

Maybe I've made an incorrect title in ttf metadata? It looks like it should be "Avenir Next, Regular" (and so on), but I'm not sure, since original fonts are encrypted, so it can't be checked.

Please help me figure out how to do it correctly, or let me know if it is still possible with this FW version at all.

Attachment 214821

Attachment 214822

Kobo Libra 2
FW: 4.38.23171

Attached Thumbnails