It's been a long road since Adobe announced its plans to phase out the Flash technology in July of 2017. For years, Flash was the target of criticism of all kinds due to its (lack of) security and performance, especially with the advent of HTML5, and browser makers had already begun deprecating support for the technology at the time.
Today is the end of the line for Flash, as Adobe has released the last scheduled update for Adobe Flash Player today. As previously announced, Flash Player will be supported through the end of the year, on December 31, but not after that. What's more, Adobe itself will block Flash content from running in Flash Player after January 12, 2021, so you won't be able to use it at all.
As time has gone on since that original announcement in 2017, more and more news have come out of support for Flash being dropped in different browsers. Microsoft announced its plans to remove Flash from all of its browsers last year, and Apple announced it would be removed from Safari earlier in 2020.
If you fear that specific Flash content will vanish from existence because of this, the Internet Archive may have some good news. Back in November, the organization announced it's collecting Flash content and preserving it through its Ruffle emulator. If there's something you want to revisit, you can check its collection to see if it's available there.