Many years ago I ran a couple of TTRPG mashups of Warhammer 40k and Dune. The emperor was much the same as 40k, the Sardaukar were marines, the Bene Gesserit were a plot manifested by Tzeentch, the Butlerian Jihad explained the lack of computers, etc., etc. It was - if I do say so myself - pretty awesome.
Now my kids are getting into role-playing and not interested in fantasy so I'm thinking about reviving my old mashup for them.
In the old days I used the 1st ed. Rogue Trader rules which seemed like the beginnings of an awesome TTRPG before Games Workshop committed fully to selling lead, then plastic, figures for skirmish wargames.
Is there a newer version of Warhammer 40k that is still TTRPG focussed, or should I dust off my old, loose-leaf copy of 1st ed. and work from that?
Dark Heresy is a newer 40k TTRPG ruleset, that might help sort of.