JSON API Filter by URL path
With JSON:API you can't filter by path because of technical limitations; JSON:API filters translate to entity queries on field values; because Drupal path aliases aren't fields you can't use the filter query param to look up articles by their alias.

A couple of different Drupal projects have cropped up around this limitation:


Decoupled Router: Provides a new endpoint where a client can query a path for any possible JSON:API resources.
Fieldable Path: Provides a new entity field (and thus queryable via the filter query param) that is designed to mimic the entity's path (with Pathauto support).


You can assess the tradeoffs from both modules and choose the one that makes the most sense for your use scenario.