Details works even when it's set display:contents too, for even more flexibility. Can't animate from open›close, yet, though. That's pretty much my last frustration with it.
I think the CSS support for that has finally landed, though it means targetting a pseudo element instead. Its been a year, so support is probably good enough you don't care if just the animation doesn't happen.
Note that the transition to `auto` in that post relies on `interpolate-size` which has yet to land on Firefox or Safari, and neither have movement right now.
