Commonwealth Fusion Systems (CFS), is the largest of the private fusion company with $2+ billion funding and 300+ employees. It is aiming to build a Compact Tokamak (ARC) using High Temperature Superconductors. The company program will first build a prototype device, SPARC, which is now starting construction. The company makes claims to have the first commercial fusion power plant in the 2030s.
More details of the CFS and other private fusion companies can be found on the page, Alternative TechnologiesCFS website