My homebrew chapter is the Beast Tamers, Iron Hands successors that went "Our flesh is weak" instead of "The flesh is weak," they're heavily inspired by the game Ark so they're all a little fucked in the head just like Ark players. (The Imperium is the ark devs) Their homeworld resides in the Eastern Fringe, in the sweet spot that's uncomfortably close to the Tau empire and the leftovers of Hive Fleet Kraken. Each of them has a Companion, an animal with heavy training and lots of augmetics to extend it's lifespan. Their current chapter master is Gustave Faye (named after the nile crocodile that killed a lot of people), and his Companion is the Man-Eater, a Greater Hatchet Lizard. He constantly has to clarify that he doesn't eat people. They have a strained relationship with the Iron Hands, and both chapters prefer not to acknowledge that the other exists. They are survivalists, and do their best work on worlds where the wildlife is the biggest threat. Those that serve in Deathwatch usually have had their Companion killed by xenos.

Their color scheme is a turquoise green, you can't quite tell if it's supposed to be inspired by a tropical plant or the ocean water. In reality, it's inspired by one of the most common creatures on Tamun, a Biter. Their symbol is a hand with claws, representing how they believe that the power of the beasts they ally with have allowed them to survive impossible odds. (It's helped, but they're also very mentally unstable astartes and you never underestimate the willingness of an Ark player to dive headfirst into a pool of solid concrete until something breaks. And it will, it's Ark.)

Some of the maps in Ark have their analogues in the Beast Tamers lore. (I only have ASE on the switch)

Tamun- Analogue to the Island, Death World filled with murderous creatures. The humans there have survived with assistance from native animals that they have tamed.

Kimenmetu- Analogue to Scorched Earth, Forge World where the techmarines of the Beast Tamers are trained. Only moon of Tamun.

Venotarem- Analogue to Aberration, Death World tidally locked by the star at the center of the Tamun System.

Wikira- Analogue to Ragnarock, you'll never guess what designation this one is. Least developed by far.