The “buildin” fonts don’t have cyrilic characters. You need to rebuild fonts in converter and then use it.
For example select Montserrat-Medium.ttf as source and set 14’s size, type 0x20-0x7F,0xB0,0x2022 as range but add 0x410-0x44f,0x451. This will add Russian Cyrilic symbols.
Then select this font as font for you object
LV_FONT_DECLARE(lv_font_my_montserrat_14);
...
{
lv_obj_set_style_text_font(label2, &lv_font_my_montserrat_14, LV_PART_MAIN);
}
Лень переводить на русский. Думаю понятно и так 