Alternative that is adobe animate but free?

​@ANtkan  already mentioned OpenToonz. 

If you ​@Nonameokay are looking for an animation production replacement for Animate: then yes OpenToonz or Tahoma2D will more than enough as a replacement. And since these are open source: completely free at no extra cost.

Tahoma 2D is a fork of OpenToonz with an optimized user experience and a number of features that OpenToonz doesn’t (yet) have.

(Keep in mind that neither Tahoma2D or OpenToonz are able to replace Animate’s interactive or development functionality. Nor do these export to any vector web formats)

Symbols

Both Tahoma2D and OpenToonz have the equivalent of what are called Graphic Symbols in Animate and are named Sub-Scenes. Just like Graphic Symbols in Animate an Sub-Scene is tied to the timeline of the document in which the symbol is placed.

In Animate converting a layer or group of layers to a graphic symbol is achieved via Modify-->Convert to Symbol. In Tahoma2D and OpenToonz this is called Collapse (either Scene-->Collapse or right-mouse clicking the timeline columns/layers and selecting Collapse).

The result is more-or-less the same: in both Animate and Tahoma2d/OpenToonz those timeline layers will be converted to a sub-timeline that is embedded in the main timeline.

Both in Animate and Tahoma2d/OpenToonz it is possible to navigate the scene depth or symbol depth.

Both apps also allow for editing these graphic symbol or sub-scene animations in-place, which means synchronizing the animation to the main timeline is easy to do.

Both also allow the animation in a Graphic Symbol or Sub-Scene to repeat automatically. Animate does this on a Graphic Symbol level, while Tahoma2D/OpenToonz achieves this on a layer level (which actually gives more control).

Both apps also allow for converting a Graphic Symbol back to regular layers in the parent timeline. In Animate this is called Break Apart. In Tahoma2D/OpenToonz we Explode the Sub-Scene.

Classic Tweens

Both Animate and Tahoma2D/OpenToonz feature an animation option that we would call Classic Tweens. 

There is, however, a core difference between the two apps in how the animator animates content via tweens.

In Animate we must convert any content to a symbol before we can tween it. If we forget, Animate will punish the animator by littering the symbol library with arbitrary symbols. So we have to create a symbol first, and then tween.

Tahoma2D/OpenToonz separates tweening from content.on a timeline layer (column). Any content can be tweened immediately without the need for symbols. Tweens operate on a different level, i.e. are “layered” on top of content in the timeline.

This is a very powerful way of working once we “unlearn” the symbol-based tweening in Animate:

• Tweens can be created any time with any content on any timeline level. 
• Tweens and their key frames can be moved separately from their content.
• Content can be changed without it affecting the tweens
• Tweens can be copied and duplicated independent from their content. It is for example possible to copy a tween from one place and re-use it somewhere else without any hassle..
• Tweens are easily removed without affecting the content.
• Since tweens are no longer reliant on symbols to function properly, it becomes a cleaner way of managing animation. 

Both Animate and Tahoma2D/OpenToonz also allow the animator to control the ease (timing) of a tween. In Animate this is done via a Tweening panel. In Tahoma2D /OpenToonz the animator right-clicks on a tween and selects the ease. 

A major difference between the two workflows is that Tahoma2D/OpenToonz adds interactive timeline controls to the tween which the animator can use to quickly adjust the ease. 

Animate adds the option to control the curve manually in a dialog accessed via the tweening panel. Tahoma2D/OpenToonz feature a fully functional graph editor to control timeline curves. (Animate’s graph editor is very limited and buggy compared and cannot be used depending on the context).

To be fair, Animate does provide a better experience compared to its Classic Tweens through its Motion Tweens. These allow the animator to quickly adjust the motion path directly in the view, for example.

Tahoma2D/OpenToonz also allow for motion paths, albeit that creating these are not as intuitive in use, even though just as functional.

Other Differences

Tahoma2D offers layer grouping/folders just like Animate. OpenToonz does not as of yet. 

One more core difference between Animate and Tahoma2D/OpenToonz is the Stage Schematic in the latter: it provides a nodal tree overview of the scene. Here it is simple to create hierarchical relationships between timeline layers and content. 

An example: to create an animated car with animated wheels the Animate animator must create a hierarchy base on Symbols. Suppose we want to animate the car movement and its wheels moving up and down as well as rotating:

Car Symbol/Wheel Symbol or Car Symbol/Wheels Symbol (up and down movement)/Wheel Symbol

In Tahoma2D/OpenToonz this is not necessary (it can still be organized like this via Sub-Scenes, though), because:

[1] the parenting can be achieved via the Stage Schematic, and;

[2] the tweening is separate from the content (no need for symbols in the first place), and;

[3] we can add empty layers and parent other layers to that empty layer in the schematic that allows us to animate multiple car parts (such as both wheels simultaneously)

While it may sound as if a Stage Schematic is more difficult in use, in practice this is not so because the hierarchy of assets in the scene timeline is easily understood.

One other core difference is that Tahoma2D/OpenToonz works with separate project files in an animation project. 

Also, Animate only supports vector-based animation, while Tahoma2D/OpenToonz allow for bitmap and indexed-coloured bitmap animation as well.

Aside from all this Tahoma2D/OpenToonz offers us a complete compositor to add various effects and output our animations directly to a publishable release. It is simply not possible in Animate. If needed, the animator in Tahoma2D/OpenToonz can combine all scenes in one master production timeline, apply various effects and colour adjustments/colour grading, and then output to one or more render outputs.

To conclude: as with any software, you win and lose some. animate can't compare in some areas with Tahoma2D/OpenToonz, but ‘wins’ in other parts.