Interesting poll. From the results so far, lots of Pentax Forums plus other photography forums, Facebook, and Youtube. Not surprising with what seems to be a fairly old demographic here.
I'm surprised Flickr isn't in the poll, but I guess it falls under "other photography sites." In retrospect I wish I had started keeping my pictures there, as it has some good "social-media-lite" features for people who actually like photography, but I already pay for a SmugMug account. The irony is they are now the same company, but their platforms are still separate. Paying for one does not get you access to the other.
I use Instagram to share my dog park pictures with the people I know at the park. It's just the platform most people are on, even though it's a pain to use and an awful user experience that just keeps getting worse as parent company Facebook tries to get TikTok to stop eating their lunch. I had wondered if my pictures were good enough to get any sort of reach beyond the people I've actually met at the park, but that's not really how Instagram works. It's a marketing platform first, social media platform second. The pictures are just incidental, and I'm terrible at marketing... and socializing.
I've never used TikTok and avoid YouTube when possible. I just don't like sitting and watching videos. I don't even have a T.V. I've never used actual Facebook, either.
Twitter sounds like a toxic cesspool I don't dare touch. I browse Reddit sometimes, but don't have an account. Too much hive-mentality bubble-building, but at least it feels friendly... if you don't sort by "controversial". I made a LinkedIn account because I read it was important, but haven't touched it in years. I still don't understand what Pintrest is. Is Skype social media? I though it was just a video phone program, which is becoming obsolete with smartphones natively supporting video calls, plus Zoom, plus Skype-owner Microsoft's own Teams.