There are alternatives, just not alternatives to what Flash (Animate) is.
Flash was always two things, animation (cutout/IK doll or FBF if you're that masochistic) and a game engine.
No tool out there replaces that functionality. Toonboom is a super over-priced program with the exact same pitfalls as subscribing to Adobe
Toonboom has cutout animation, it is not a game engine.
Spine is an animation tool designed for games. It is not an authoring program, you still have to import png's from another program.
Most animation tools out there, from OpenToonz to Blender grease pencil, are FBF animation tools, not cutout animation.
Synfig maybe works the closest to how Flash works, working in vectors, it does not actually produce animation itself and relies on FFMPEG.
Like 90% of the problem with the vector workflow is the SVG standard which doesn't attach useful metadata to the shapes to render them consistently in all software packages in order to animate it.
Moho is probably the best commercial software package available that has a perpetual license, and even then at $400 it's basically the same price as Animate(Flash) was when it was a stand alone product.
Krita and CSP have animation functionality in them, but it's not designed to actually produce more than a few seconds, because they are paint programs with some extended functionality, all the actual animation ends up having to be done in premire pro, davinci resolve, final cut, or something else.
Like it has to be said repeatedly that the FLA files from Flash/Animate can not be opened in any program. They are basically zip files full of binary objects that can't be read. And Adobe's suggestion to export a .swf file, means a 300MB project easily turns into a 3MB binary that can't be decoded back into something editable. Even then there is a decompiler out there that lets you do exactly that, but it often makes mistakes on anything complicated or containing actionscript.
But that decompiler can't create a project for another program, because no other program can play actionscript.