New release: 2.1.7+ds-2~ubuntu20.04.1
I finally managed boldface issues. So the app correctly chooses Open Sans of Semibold style. Although, still remain troubles with Italic style in the input box. But I think this is a minor problem since 2.0.1+ds-1build1 currently available in focal has the same problem. (In the input box, Telegram Desktop does not use Italic font style, instead it takes Open Sans Regular and tilts it).
I have reverted Hunspell integration to not break user settings in existing installations.
Edited by Nicholas Guriev