I tried to install Opera on Ubuntu 20.04 this morning (5 January 2021). It got stuck trying to install Flash (Pepperflash). It kept trying to download from adobe.com, but, of course, it couldn't. After much fiddling, I got it working. But I get warnings:
coddpkg: warning: files list file for package 'pepperflashplugin-nonfree' missing; e_text
Whenever I start Opera, I get a message asking if I want to disable Pepperflash. This happens every time.
As I mentioned... I got it working, but it really was a battle. Can you please disable Flash in the installer?