That said, my kid, above all else, had the most fun with paintz.app (website), just creating pictures. He's moved onto brush.ninja now (at 7) and is doing simple gif animations. Source: over 1 year ago

I wasn't sure if that was allowed. The site is brush.ninja, I shall update the original post to show this too. Source: about 2 years ago

Https://brush.ninja/ is fast/nice if you just want to do quick stick figure type animated gifs. Start by drawing something simple in the current frame, then down at the bottom, use the "duplicate" to make the next frame and add some changes. - Source: Hacker News / about 2 years ago

I can suggest brush.ninja for online (2D) animations or OpenToonz/FlipaClip for downloadable software animations, along with Blender for 3D animations (all of these are free to download and use). Source: over 2 years ago

The only thing I know with half of those features that's discontinued is the old Darkroom app but that doesn't tackle some of the bigger compatibilities. Source: about 2 years ago

Not sure if this is applicable, but if you're using Word or Scrivener or something, you may want to switch to a plaintext editor like Dark Room or Typora--something that won't underline your spelling and grammar mistakes. It doesn't even have italics or bold to get in your way. Dark Room is a little old, but I found it here: https://codex.jjafuller.com/books/dark-room/page/overview. Source: over 2 years ago

I use DarkRoom. Full screen, no distractions, no "fancy" auto-formatting. Source: about 3 years ago