Are questions asking how to do something in a web browser, which either implicitly or explicitly must be accomplished by a plugin, considered on-topic? That is, should we accept questions like this?
My inclination is to say that this is on-topic, since such a plugin is software running on Ubuntu, we support third party applications anyway (so why not third party plugins?), and there are substantial differences in what plugins are available and how well they work, from platform to platform.
But I'm interested in seeing what the community thinks, as it's been suggested that this question should be closed as off-topic.