Tried opening opera earlier (67.0.3575.31), it just hanged and I had to end the program.
I reinstalled it after renaming the profile folder, it was fine while I was doing all the settings, but when you log in to sync it hangs again.
I checked on another computer and the same thing happened, it also happens on older versions so it must be sync causing it.

@leocg I don't know if you are running the beta or developer version of Opera, I am on 73.0.3856.329 which is up to date, and I get this popup multiple times a day:

So stop replying with wrong information.

@sgunhouse the message is definitely from Opera, windows is not putting up any messages about flash. If I had one of the plugins installed I would have got this message:

@leocg - Do you know anything about what you are saying, you should be more informed before you comment on something. I do not have any plugin version of flash installed. Windows 10 20H2 has flash built in to the system. Windows was fresh installed two weeks ago.
To quote from Microsoft:
"In the new Microsoft Edge, Adobe Flash Player will be removed by January 2021. An update titled “Update for Removal of Adobe Flash Player” will be made available via Microsoft Update Catalog, Windows Update and WSUS that permanently removes Adobe Flash Player as a component of the Windows OS devices."
Opera is the program displaying the popup, there are other posts from people on this forum complaining about the same thing. Opera is ether detecting that version or just continually popping up the same reminder with no way to remove it.
Now instead of wasting my time, do something constructive about it.

Yes we get it, flash is gone (going....) Microsoft is dragging its feet removing it from windows completely through windows update - they should have removed it on 01 Jan and be done with it.
We all know its going, so can you please let us disable that damn annoying "Flash Player will no longer be supported after December 2020" popup message.

Tried opening opera earlier (67.0.3575.31), it just hanged and I had to end the program.
I reinstalled it after renaming the profile folder, it was fine while I was doing all the settings, but when you log in to sync it hangs again.
I checked on another computer and the same thing happened, it also happens on older versions so it must be sync causing it.