Not in the UK, it isn't. You're assuming Prime Video offers the same content in all countries. It doesn't. Andromeda isn't even available on Prime Video in the UK to rent or buy.
It was available On Demand for the Pick channel in the UK and Ireland as of last year (and in high definition, too, I presume from the recent-ish Blu-Ray release), which I used to do a full series watch through.
It's not up there anymore, though, admittedly, but I think they still do reruns on that channel and others. It
used to be on Netflix over here, but that was many years ago. (I enjoyed doing the full series watch through mostly because of how fond I am of the program, in spite of everything that happened to it and that the show could never live up to the
idea of what it could be that Robert Hewitt Wolfe's "Coda" leaves one with.)
Actually, forget what I just said. Calling
Lexx porn is an insult to porn.
Better to just call it Eeeeeeewww and be done with it.
Honestly, Lexx is both a great and terrible show. It was very committed to its weird aesthetic, bizarre cosmic scale and dark sense of humour; and in its best episodes - like "Brigadoom" in season two and "The Game" in season four, or particular the arc that ran throughout season three - it was something odd and special. Unlike Andromeda it had a lot of the same team behind it throughout its four seasons and thus has a more consistent if much more looser and fantastical sense of self.
The worst episodes are however the worst television I've ever sat through, and a lot of that has probably aged poorly (the homophobia, for example) and yet I'm incredibly fond of the Lexx that wasn't terrible. It's not really something I recommend but it's also something I think about all the time.
An interesting point of comparison between Andromeda and Lexx is while each had a scope that spanned galaxies at their inception they both spent their final seasons with the title ships mostly spent of power and energy, trapped inside a single solar system.