Noticed the same issue with latest update to Opera v55.0.2994.37 on Linux Mint 19 Cinnamon (all updates installed). Was working fine in all previous Opera versions - ie. could click outside Whatsapp or on the Whatsapp icon to close the sidebar.
Latest posts made by sleepyeyes
-
RE: Whatsapp plugin won´t close.Opera for Linux
-
RE: [Linux Bug] WhatsApp on new sidebar: doesn't hide when I press the icon againFuture releases
Noticed the same issue with latest update to Opera v55.0.2994.37 on Linux Mint 19 Cinnamon (all updates installed). Was working fine in all previous Opera versions - ie. could click outside Whatsapp or on the Whatsapp icon to close the sidebar.
However, contrary to the OP, I find that I can still close it by pressing Ctrl+Shift+M.