Here is a free software animator: https://www.synfig.org/

Development is kinda slow, but this also means that it still works just as well as when I made a little short movie 15 years ago.

Thanks, I never heard of this one, will try it out.

One very interesting new one is rive.app Closed app, free for 3 files, but open source renderer and GPU accelerated.

Yeah, me too. Why, just why didn't Adobe open source (and vastly improve in terms of security) the flash player and rather let it die. It was such an awesome ecosystem.