Here too, as of a few days Opera is stealing keys:
Ctrl-shift-backspace
Ctrl-shift-end
Ctrl-shift-home
Ctrl-shift-insert
Ctrl-shift-page-down
Ctrl-shift-page-up
Very simple to verify:
download Nirsoft - HotKeysList from https://www.nirsoft.net/utils/hot_keys_list.html
launch HotKeysList with Opera not launched -> these keys don't appear in the global hotkeys list
launch Opera -> the keys are added to the global active hotkeys (press the refresh button to see the active keys list change immediately)
exit Opera -> the keys are removed from the global active hotkeys
And I don't even know why it's even doing this (so that I can try disabling the behaviour). I suppose that it's something to do with mediakeys, but disabled "Hardware Media Key Handling" and "Experimental system keyboard lock" in opera flags but no change.
These keys are used all the time in other programs, so if this doesn't go away quick, it seems that after some 20 years I'll finally stop using Opera, something that even all the removed functionalities that happened when they moved to the new chrome based builds hadn't been able made me move.