Can't speak for OP but my spouse has set up a private GroupMe for posting events for a group, but otherwise everyone shares pictures using text messages. We don't post any pictures of our kid where strangers can easily get access to them and we've read the privacy policy of every service we've ever used.

I was considering self-hosting something for a while but she found it more sensible to do it this way.

Every once in a while she logs into Facebook to post something on Marketplace and immediately gets completely sidetracked by their algorithm and design. Then she gets frustrated and we just put the thing she wanted to sell on the corner instead.