To my knowledge Scripps Networks (HGTV, Food Network, etc.) have never paid back end royalties, but are instead ‘buy out’. I’ve never worked for a library catering to these, so I don’t know exactly what that looks like for composers, but I’ve always avoided them personally.
There was a big potential blowup that happened when they merged with Discovery Networks… Discovery threatened to adopt their model and stop paying back end, but there was a major revolt amongst libraries and composers and they eventually backed off that idea (thankfully).