There is no alternative plugin to Flash Player. The alternative is for content providers to migrate their content away from Flash dependency on to some other technology.
The most recent verssions of Chrome and Firefox no longer support Flash Player, as browser vendors have dropped support for Flash Player after Flash Player's end-of-life at the end of 2020.
For completeness:
Adobe announced Flash Player's end-of-life in July 2017 giving content creators, programmers, developers, IT experts, etc over 3 years remove Flash Player dependencies from their products. All modern browsers provide the capabilities necessary to do this in JavaScript. This is an investment and prioritization choice, not a technical limitation.
For reference:
Major browser vendors are deprecating Flash Player support. Details specific to each vendor:
- Apple Safari - removed Flash Player support in Safari 14, released Sept 16, 2020
- Google Chrome - removed Flash Player support in Chrome 88, released Jan 19, 2021
- Firefox - removed Flash Player support in Firefox 85, released on Jan 26, 2021.
- Firefox ESR 78 will support Flash Player for the time being, assuming the Flash Player NPAPI plugin is already installed as it’s no longer available for download.
- Microsoft Edge - removed Flash Player support in Edge 88, released Jan 15, 2021
- Microsoft Internet Explorer and legacy Edge - Has information on options for continued support for enterprise customers