If you need to output a signal elsewhere, as other people have mentioned the only option is via a HDMI Splitter and a HDMI to SCART or RCA convertor.
Such as
https://www.amazon.co.uk/iSolem-1080.../dp/B006KZBC92
https://www.amazon.co.uk/Neoteck-Con...=hdmi+to+scart
https://www.amazon.co.uk/Tendak-Comp...omponent&psc=1
The
key thing is that the Tivo will have to be set to output the correct signal via the 'test' option.
I don't have my v6 and Slingbox hooked up to a 4K TV, but I'd think you can't have 2160p as an output option on the Tivo.
I know by default the Tivo outputs 1080p at 60hz and I had to down it to 30hz as Slingbox doesn't support 60hz.
Yes the V6 doesn't have a scart socket, but really it's not the end of the world