How to prevent images from shared collectios to be downloaded

This is the internet. If you can see it in a browser, you can steal it. There really is nothing you can do about that to completely stop it. You can't stop screenshots and you can't completely prevent saving the image even with javascript. If you can see the image, it means it is now stored on your computer/device and you can get the browser to save the images in a different spot. Absolutely nothing you can do about it and nothing to do with Lightroom. Lightroom web could make it a bit harder to save the images you see in the browser, but it cannot be completely prevented. This is just the way the internet works and you really can't stop this. When people do it it is still copyright infringement and applicable laws such as the DMCA in the US apply however! This is true also for the AI people when they use internet material to train their AI bots and there are a number of lawsuits in the courts around this that still need to be resolved and from what I hear very well might go the way of the copyright holders but that is currently still unclear and it is still the wild west out there.