Does Sidekick Still Exist?

No, Sidekick was acquired by Comet Browser (by Perplexity) and they shut down Sidekick as a result.

Does Sidekick Browser Work on Windows?

Sidekick Browser works on Windows, MacOS, and Linux.

Does Sidekick Browser Have a Mobile App?

Sidekick is a desktop-only browser, they have no plans on adding a mobile app and doesn't seem likely that they will add it in the future.

Is Sidekick Browser Private?

Sidekick Browser uses Chromium as the foundation like most other browsers out there, so the level of privacy stems on Chromium being at the foundation. That said, they do go a step further and have a baked in VPN service and they claim to never disclose users' search information. That said, you probably are no more or less secure or private using Sidekick as you would be with other browser on the market like Arc Browser or Firefox.