@manuzzi
Found a solution here: https://askubuntu.com/questions/1224125/font-characters-displayed-as-squares-in-ubuntu-18-04.
But recently the problem came back.

@rm-arunhoney Yes, check https://www.opera.com/download

dpkg-deb --contents opera-stable_75.0.3969.93_amd64.deb|grep -i widevine

-rw-r--r-- root/root 125 2021-03-23 04:00 ./usr/lib/x86_64-linux-gnu/opera/resources/widevine_config.json