I haven't had Instagram account for a while anymore, but I haven't stopped posting online random photos I take. During the past year or so, Pixelfed has grown to be a viable alternative to Instagram.
Pixelfed is similar to Mastodon that it forms a federated network of autonomously maintained server instances. You can join any of the open instances or even setup your own and begin to federate with the others.
Pixelfed has adopted many of the features users of Instagram are fond of, such as "stories", but all without the heavy advertisment push. You can find me on Pixelfed.social instance.