As spotted by PCGamesN, a new add-on for Red Dead Redemption 2 called "Vestigia" overhauls a lot of visual and environmental aspects of this enormous game. As described on the Nexus Mod page, users no12, DayL, WhyEm, and Majestic253 have essentially created four mods all rolled into one. Some of the features that the whole download comes with include a more "connected" weather system, in which transitions are more natural rather than jarring. It also implements better world flora, as well as changes in the AI of animals and humans. This also includes adding additional pedestrians to cities, with them being more likely to talk to one another.
I bought this game about two years back on a Steam Sale, and have still not got around to actually installing and playing it. It was on my bucket list, so made sense to buy, but I've still been totally absorbed with SnowRunner. It may have been worthwhile holding off, I think, if I can also get these mods to work (on Linux that is). As it was, the game was already sensational in its detail - so much so, I used to just watch the YouTube play throughs.
See Red Dead Redemption 2 Mod Makes the Game Look and Feel More Realistic
Red Dead Redemption 2 is already considered a very realistic game in terms of its visuals, but evidently these modders feel it needs something more.