Adobe says that once Flash reached the EOL date, the company doesn't merely plan to stop providing updates, but they also plan to remove all Flash Player download links from their website.
This will prevent users from installing the software and continuing to use an unmaintained version.
Furthermore, Adobe also said that "Flash-based content will be blocked from running in Adobe Flash Player after the EOL Date," suggesting the company has added or plans to add a so-called "time bomb" in the Flash Player code to prevent users from using it starting next year.
These are some of the most aggressive decisions a software company has taken to block users from using its software once it reaches EOL.
The reason for these moves is because Flash Player has always been targeted by hackers and malware authors. Once Flash Player reaches EOL at the end of the year, Adobe doesn't plan to provide new security updates, leaving Flash users exposed to new vulnerabilities and attacks.
The optimum scenario for Adobe would be to get as many users to uninstall Flash Player as possible before December 31, 2020. It is unclear how this "prompt" will look like, but users can uninstall Flash Player right now by following these uninstall instructions for Windows and Mac users.
Flash Player usage has started dying out in 2017-2018
Speaking at a conference in February 2018, Parisa Tabriz, Director of Engineering at Google, said the percentage of daily Chrome users who've loaded at least one page containing Flash content per day has gone down from around 80% in 2014 to under 8% in early 2018, a number that has most likely continued to go down in the meantime.