What to do to replace adobe flash?

Web Masters should be converting their web pages to HTML 5 Video.
Your Browser already supports HTML 5.

HTML5 and CSS3. Flash has effectively been replaced for most sites already. About the only sites that haven’t been updated are the legacy Flash sites that “no one” cares about, like old Flash games and sites that simply aren’t going to bother updating.

If you wanted to continue using Flash content, you would need to either install an alternative browser that continued to run the plugin, install an add-on that emulated Flash, ask the website to emulate it, or wait for the content to be ported over.

Flash can be emulated to some extent with browser add-ons like Ruffle. Newgrounds already implements this without an add-on for much of its older Flash content. Note that it cannot currently run ActionScript 3 content, which is the stumbling block all Flash alternatives seem to run into.

https://ruffle.rs/
https://www.newgrounds.com/portal/view/59593 (example game)

If you need full compatibility with Flash, your only real option right now is to install a browser that still supports traditional plugins, like Waterfox Classic. It will continue to support NPAPI plugins after Flash is discontinued.

https://www.waterfox.net/download/