Bold text in Telegram Desktop changed to bold italics

Hi all, this is actually a minor problem but still very annoying to me. I installed Telegram Desktop from the official repo. The program runs without problem so far except that texts that is supposed to be bold fonts like contact names, group names, channel names, etc are shown with bold italics fonts. I have tried installing the flatpak version and that one doesn’t have this problem. I tried to launch the app from command line, it gave no useful message.
I use latest KDE Plasma.
Anybody what caused the problem and how to fix it?