A: We have solitaire rules for Fluxx (adaptations available for pretty much any version).
Solo Fluxx FAQ

Chrononauts and Early American Chrononauts have a very good solo version as well (rules for Solonauts are on the second page of the Chrono rulesheet PDF). Here’s our (rather long!) Solonauts sample play-through video (playing with the EAC deck, in this case.)
Solonauts FAQ

There are also lots of possibilities with the Looney Pyramids. For example, included in Pyramid Arcade is Andy’s Color Wheel, which can be played solo.

Beyond that, there are many fan-designed pyramid solitaire games. We can’t guarantee that all fan-made games are awesome (or even finished, in some cases!) but there ARE some awesome games among those, so check them out!

If you’re interested in the pyramids, you might also consider joining the Starship Captains group on FB and asking fans there what their favorite solitaire pyramid games are.