Shutter-Time-Calculator VS photo-stream

(Online calculator https://calc.loef.photos/ says 20/15/7 seconds max for it's rule of & npf calculations: 500 (major)/300 (slight)/200(pinpoint))

Without a tracking mount you can use this calculator to determine what exposure time you can get away with without significant trailing. It depends heavily on the declination (basically the arc length between the north pole and the object you are pointed at), lens focal length, and pixel size of your camera.

This was a 14mm lens, most will say use 500 rule but I suggest you to use NPF rule if you want pinpoint stars(or it will have an option like slight trailing this is what I used) it showed 12 seconds I think, I went a bit over since I know 14mm is pretty wide and you can't see any trailing once it is wide

That method isn't that accurate anymore(some people use 400 or even 300 rule), but these days the recommended method is The NPF rule.

4) How to select your exposure length: If you take long duration exposures (let's say) 15-20s or something, what you will see are star trails where instead of pin pointed stars, you'd see them moving in a line, ruining our shot. To get sharper stars, either use the rule of 500 (beginner friendly) or the NPF rule (more accurate, but a bit more advanced). Make sure you take a few test shots, zoom in and check the focus and star trailing first before continuing.

I've made a Calculator some time ago that can help you decide on the expose times without a tracking mount. It might be usefull: https://calc.loef.photos/

Seeing might have also been just not good enough. I saw an app called nightshift. Pretty good indications of how clear the sky is actually. Also, indeed have a look at the 'rules'. 500 rule might be a bit too crude. Suggest to check your camera and lens specs and fill them in at: https://calc.loef.photos/

First thing I thought of are applications like Photostream. But I thought maybe someone knows of an even better application for my usecase, or has their own experienced to share. (Photostream doesnt support videos though for example).

Currently using photo stream

While photo-stream does not officially support subfolders it could probably achieved with some manual work or a custom script. There has been a short discussion about it here.

Not 100% sure but I think PhotoStream can do what you want. You could mount the shared folder and ever time a new photo will be dropped it should update the static page which also allows downloading a photo if you set the config for that. Depending on your setup you might have to automate syncing if you need that.

If you just want to showcase your photos on a static page have a look at Photo Stream.

For something simple you could check out photo-stream. I think it's good for an online portfolio of your work.