Mark from The Retro Channel has created a board for testing video signals with an oscilloscope.
It has video and audio inputs, including a SCART connector. Each signal is output to stubs for oscilloscope connection.
Mark notes that the board can be used as a SCART to RCA (or S-Video) adapter if the 75 ohm termination jumpers are removed. It is not intended as a replacement for specialty adapters, but may be useful in certain situations.
Mark sells fully assembled versions of the board in the Tindie store at The Retro Channel https://www.tindie.com/products/theretrochannel/video-debug-scart-breakout-board/ for $35.