If people need alternatives to 500px, Flickr allows CC-licensed photos, and recently got sold to Smugmug. Hopefully they'll keep the licensing intact.
One of the things I prioritise when picking a platform is answering the question "how easy is it to leave?". Flickr still seems pretty easy to leave if it comes to it.
As someone who is not a photographer, I only follow photographers on Instagram. FWIW.
Flickr is much more relaxed; it's not perfect ( you can't exclude photos fron the Photostream for example ) but there's less of an expectation of consistent performance. I'm happy to upload 'warranty shots' to Flickr, unexciting but interesting documentary photos.
It's still a liberal/free license but they're now using a custom license under their control and have also accepted 7.25M funding round so they could also become hostile in future. For this reason I'm hesitant to rely on their APIs and only maintain and use offline copies of photos I like.
> The funds being invested today will be going toward defining a new economic model around photography. It won’t be a model where photos are going to be paid for with cryptocurrency. It will be a model that leverages the unprecedented distribution Unsplash photos gain to bring as many opportunities to contributors as possible while maintaining the open, free-to-use principles of the community.
- https://medium.com/unsplash/we-just-raised-7-25-million-for-...
https://fstoppers.com/business/why-you-should-never-upload-y...