@RedLenai mentioned Artstation and Furaffinity and I want to share a bit of insight on these 2
Furaffinity is very hands off with NSFW stuff altho it comes with a few caveats: it shrinks your file, and browsing it is not for the faint hearted lol.
Artstation is good as a true professional portfolio, but I'm not sure what their stances on NSFW content is. I know they don't allow anything NSFW for artwork icon, but they do have a mature content toggle when you post.
Imgur is good, you can set an album (posts they're now called) as private and probably post whatever, but they keep changing their UI and both the app and the mobile versions are kinda useless if you want to do anything beyond browsing. Also they turn any file bigger than 5MB to JPEG.
I personally use Weasyl to archive my art, it's an out of the way site somewhat similar to Furaffinity and Deviantart, but a bit less unhinged than the former, and afaik they allow anything except like, nsfw photography as long as you use the provided warning options. You can upload files up to 50 MB in size. You'll need to have someone vouch for your account when you sign up so you can use the site fully (an anti spam measure), but you can I think email support to do it for you, or you can DM me with the link to your account and I can vouch for you if you decide to try it
)
Twitter allows NSFW, but being a major social media platform, who knows when that will change. I mean look what happened to Tumblr.