There is Goldfish, which was started with beeing some sort of TikTok alternative in mind. But it's stuck in a very early stage and doesn't seem to be developed anymore. If I remember correctly the Admin started it as a practice for themself to get more into Activity Pub.
They have a Mastodon account and a github page, maybe you can ask them there if they plan to develop it further. And since it is open source and can be forked by anyone and everyone can contribute to it, maybe someone will be found who is interested in continuing to work on the project.
On Goldfish's github page I also found Vidzy by accident, where developement seems to be more active. However, I found no active instances so far where one could test it.