How well Nouveau works depends on the actual video card. Some work perfectly,
others have problems. My understanding is that upgrading the kernel can be
necessary for some of them to work properly.
Gnash only works properly for streaming YouTube videos, where it works just
fine. The Firefox extension UnPlug works for some others, and you can stream
with it by "opening" certain files (Ogg and WebM files can be handled
directly by the browser, while MPEG files can be handled by a plugin that
works with Totem). This works really well, and I actually use UnPlug for
YouTube instead of Gnash, since I don't want to use YouTube's nonfree
Javascript. You can download UnPlug for Firefox on whatever system you're
currently using to see if it works on the websites you want it to.
Actually, with Trisquel 6, I think the biggest problem you would see is that
Wine seems to be broken; you can't install it from the package manager.
Hopefully this can be fixed at some point.
