Red Dead Redemption 2 on PC has a number of advantages over the console versions, teething problems aside. Better visuals, more content, but arguably of the most use, a better chance at fiddling with the game files. Digging through the game data has already yielded a particularly interesting discovery - there is a fully animated and textured Caveman character model in the game.
Discovered using the Lenny's Simple Trainer tool developed as a cheat engine for the story mode of RDR2, the Caveman skin is referred to in-code as A_M_M_UniCorpse 01. It isn't clear where players are supposed to encounter this model in the game (presumably as a corpse, based on the file name), but it might also be cut content which doesn't end up being visible unless using the trainer. Whether or not it's present at all in the consoles versions cannot be known.
The initial discovery was made by Reddit user thatfalloutguy while flipping through variations of possible character skins they could make Arthur turn into using the trainer. Being a full character skin, you cannot dress up the Caveman in the game's clothing options, shave him, bathe him or do anything that alters his appearance.
There are also a few minor bugs when using this trainer. If you are "wearing" the Caveman, sitting down will trigger the red damage indication tint on the screen. You should also make sure that you have autosaving turned off when using the trainer, and absolutely do not play Red Dead Online with it installed because you will be detected and banned.
Other than that, this skin selection trainer can lend itself perfectly to some experimentation with the in-game photo mode. There are several locations with cave paintings, and you can also capture scenes of the Caveman foraging for food or hunting wild predators!