Strange that I can still find Roberto Soldic profile page on KSW website and ONE Championship pages.
I am not sure he made a good decision moving to ONE as his new organization, but maybe they offered him more money and deal he could not refuse.
I see this new boxing fight against Adamek is under Fame MMA organization, this is the first time I hear about them.
If you take a closer look at his KSW page, there's a little note saying "Former fighter" right under his name. It seems like the KSW lists all their fighters, former and present, which is quite nice.
Fame mma is a Polish "freak-fight" organisation with a lot of controversies around their shady and unethical practices. Their business model was to match up celebrities from you tube or social platforms by offering them good money. Since the fighters are already somewhat famous, it doesn't take much to hype up such fights. It seems that the business model paid off. They are now expanding a bit and taking on board actual, trained, professional fighters. Soldic and Adamek are good example.