All the major browsers will no longer support the flash player, in any way from the end of 2020.
At the moment most browsers require the flash plug-in to be enabled via a browser setting for each and/or every site, but unless your clients are only using it via an intranet and are not general internet users, you should work on the fact that you cannot ask normal intrernet users to enable the plug-in from today. Even though the plug-in can be enabled, over the next few years the restrictions will increase until it can no longer be used in a browser.
As Paula said, the official end-of-life for Flash Player is late 2020. But I can tell you from personal experience that getting Flash Player to work right now with modern browsers is like pulling teeth. You have to go through so many hurdles it's hardly worth the trouble anymore. Safari, MS Edge, Chrome & Firefox are all phasing out plugins. That's the reality.
If you're still using Flash media I think it's fair to say you need an exit strategy right now. Don't delay.
the time to finish using Flash was about 2 years ago... get out now!
Thanks everyone for the replies. Time to get to work and migrate from Flash!