After Filmation's awesome Flash Gordon cartoon series and before Filmation's He-Man cartoon series, Filmation made BLACKSTAR. And it is absolutely the midway point between those two cartoon series. It went 13 episodes and didn't get picked up for a second season. Because of the popularity of He-Man, and because of how similar the two cartoons were, Galoob put out a Blackstar toy line hoping to cash in on the success of He-Man. 

Toy Galaxy/Secret Galaxy did a whole history of Blackstar covering all of this a couple years ago. Which is where I found out about the French Blackstar comics. 

There's a big comic that is hard to get a hold of in the US, but the anthology comic magazine PIF GADGET had a bunch of issues that included short Blackstar comics. 

-Pif gadget n°846 story : "Le naufragé du cosmos".

-Pif gadget n°852 story : "La forêt de cristal"

-Pif Gadget n°854 : "La tempête de feu"

-Pif gadget n°859 story : "Le monstre de boue"

-Pif gadget n°860 story : "La flûte de magie"

-Pif gadget n°866 story : "La conque d'or"

-Pif gadget n°867 story: "La conque d'or: la meute des monstres"

-Pif gadget n° 868 story : "La conque d'or: le choc des épées"

-Pif gadget n°873 story : ""Le territoire des vampires"

I've managed to buy all of these issues on eBay except 866 and 868. But I might have managed to buy 866 tonight on some other site. I'll see if it shows up.

Another Mattel toyline with a cartoon, Jayce and the Wheeled Warriors, has a 15 page story in issue 922 of Pif Gadget. 

And that issue is on Scribd. 
www.scribd.com/document/262694295/Pif-Gadget-922

https://imgur.com/a/pbOrPnY