Trisque does not make easy to install the proprietary Flash player, what is
good. If you have not worked to install it, it is not installed.
Gnash, a free Flash player, is installed by default. You can remove it if you
want, for instance from the "Synaptic package manager" in the "System
settings".
Here is the relevant documentation to play videos in your Web browser without
using Flash: https://trisquel.info/en/wiki/play-videos-without-using-flash
I personally use ViewTube and ViewTube+ and I try UnPlug as a last resort.
