Other companies are working on reuse, but they haven't gotten anything up and running.
Neutron, Terran R, and New Glenn will have reusable 1st stages. New Glenn will probably fly first in the next year or two, but we'll see how long it takes them to reuse a stage.
Stoke is the only one I know of working on reusable upper stages. They actually hopped a prototype of their upper stage not too long ago.