As of December 31, 2020, Adobe Flash is end of life. It has been removed from gentoo.git in bug #754192.
Alternatives to Adobe Flash may be available.
An alternative to using Adobe Flash Player when only playing video streams from YouTube, Vimeo, Twitch, Internet TV stream, etc., is to install media-video/mpv with the
lua USE flag, and media-video/ffmpeg or media-video/libav with the
openssl USE flag. The
lua USE flag allows net-misc/youtube-dl to work in mpv, and the
openssl USE flag allows FFmpeg/Libav to open https:// streams. Next, install the Open-with Firefox add-on and configure it in the following way:
- Open about:openwith, select Add...
- In the dialog select a video streaming capable player (e.g. /usr/bin/mpv).
- (Optional step) Choose how to display the dialogs using the left panel of Open-with add-on.
- Right click on links or visit pages containing videos. If the site is supported, the player will be open as expected.
The same procedure can be used to associate other video downloaders such as net-misc/youtube-dl.