Oh, and for what it's worth, I was still unable to get the Retrotink to display anything other than 15 KHz modes on the LCD display. I got either a black screen or the "no signal" color bars that the Retrotink generates on boot. All 15 KHz PAL and NTSC modes still render fine. It does seem odd that it's not able to pass through things like the 30 KHz 640x480 and 640x576 modes, but the Amiga adds a little special something that the Retrotink isn't keen on, it seems.
...oops. It helps to read the docs:
https://www.retrotink.com/post/we-re...h-new-products
The SCART unit does not have a pass-thru mode; only the latest "2x Multiformat" product includes that. So that explains any mode that doesn't need line-doubling not working.