We have mobile (iOS/Android) SDKs, so you can use LD for mobile apps as well, but the backend SDKs are primarily meant for SaaS-style server processes (where the SDK token can be guarded from users, and the process serves many different users, some of whom will get different flag values).

We have gotten some requests for desktop SDK support, which would work more like the mobile or JS clients work, since there is a single user at a time, and the key used to get flag values must not leak any proprietary business info or details about other users. This is on our roadmap, so the funding will help here :)