Thundarr was also one of the first I thought of, and I went down the same rabbit hole, although I knew there had never been an official comic, was hoping at some point there was at least a promo or mini-comic, or at least something celebrating the animation, Kirby's style guides featured on the cover, or some Alex Ross homage cover?
Instead, like you, came across several of those fun, fake covers.
Love it when it's the fans that do a better job of keeping a franchise alive, then the rights holders.
it's sad that Thundarr, Arial and Ookla and their great setting and concept were never given a series.
Was hoping at the time Future Quest was being developed, they'd run a parallel launch for Ruby-Spears universe. .