It does not work for me either way:
lv_label_set_text_fmt(lbl_temp_mv_canvas, "%s %c C", pBoilerTemp->s, 0xB0); lv_label_set_text_fmt(lbl_temp_return_canvas, "%s °C", pReturnTemp->s); /* from line 1596 monts_26 */
Do not know why, I can see it in the font I use.
Thanks.