First and foremost… I would check into buying used from a reputable reseller that guarantees their equipment:

usedphotopro.com

www.mpb.com

www.keh.com

IDK where you’re located geographically, but a couple of those do ship to different countries so they should have you covered.

As for your specific camera needs, it’s going to depend on the setting you’re taking these pics in. It’s less about subject (nature, graffiti, consenting butts) and more about speed and and light levels.

You’re right that taking a frozen moment from a moving vehicle you need a fast shutter (this is different from a “fast lens”). Most modern digital cameras should have no problem getting a fast enough shutter speed… something that tops out at 1/2000 or 1/4000 should be plenty. The farther away it is, the easier it will be.

Nature pictures like landscapes are generally pretty easy to shoot. They don’t move around much so you have plenty of time to set things up and find your scene. Nature pictures like animals… that’s a whole other story and takes specialized stuff usually, depending on the animal. The good thing is that with interchangeable lens cameras, some of that is just the lens and can be upgraded when you figure out which niche you’re trying to fill.

When you get into these types of cameras, you are really buying into a lens system… that is a good place to start thinking about it. Will you be able to get lenses you like for a price you can deal with. Often that means not only how are the first party lenses, but are there good third party lenses. So take canon for example… great first party pro lenses, crap entry level lenses. Their DLSR has access to stuff like Sigma which are really good… their mirrorless they more or less banned 3rd party so you’re sol. So a little research on that is a good idea.

So my suggestion, personally, is to look at micro-fourthirds flagship cameras from the last decade and flagship DLSR as well. You will get a lot more bang for your buck and quality from an older flagship pro camera for the same price as an entry level new camera. There is a hidden price advantage for M43 cameras as well… the lenses are cheaper, lighter, and since it’s an open format there’s lots of choices from multiple manufacturers. If you get an Olympus camera, the lenses work on Lumix. If you get a TTartisans M43 lens it works on both. So you have a lot of choices for very inexpensive. Basically all M43 cameras have In Body Image Stabilization as well… which is really nice for getting rid of camera shake while taking handheld shots in lower light.

As for software. There is plenty of stuff that will work well on linux… and lots of them are likely in your repos already or have flatpak or appimage. I really like RawTherapee for processing RAW images. www.rawtherapee.com There are some good scripts to get Affinity Photo working on linux these days as well such as github.com/ryzendew/Linux-Affinity-Installer … just read thru the info thoroughly, but it’s basically run shell script and click buttons on the GUI.