More recent versions of Photoshop have a frame-based editing setup that can be modified by hand, allowing use of filters and similar tools. This feature has essentially been ignored by every commercial alternative to Photoshop (Affinty, Pixelmator, etc.), which is why I don’t use them. I edit a lot of GIFs.

Krita allows you to import videos or even other GIFs as frame-based animations, which you can then modify to your desire, even adding things like filters or layering images.